Wood/Glass/Metal Seeking a cheap wide mouthed jar capable of withstanding a vacuum

[joniverson]

I'm looking for a cheap, wide mouthed jar capable of withstanding moderate vacuum (up to 29-30" Hg). The jar I've currently been using is like http://packagingoptionsdirect.com/8-oz-french-square-clear-glass-bottle-028047?gclid=EAIaIQobChMIqMnmme_g2gIVgUSGCh3frw2_EAQYAyABEgKgG_D_BwE one with a rubber stopper and plumbing valve in place to hold vacuum once evacuated, which works well, but I now need something in a 3-4" width but not any larger really (no more than 16 oz size). A first thought is a Mason jar with a suitable rubber stopper for the top, but I don't know if they could attain and hold that sort of vacuum for a month (the French square jars easily do). Budget is limited, otherwise I'd just have a suitable vacuum desiccator chamber. The French square jars come up to 32 oz at good prices, but the mouth still isn't wide enough. Thanks in advance.

Jon

 

[berkeman]

Thread closed temporarily for Moderation...

 

[berkeman]

Thread reopened provisionally.

I'm looking for a cheap, wide mouthed jar capable of withstanding moderate vacuum (up to 29-30" Hg). The jar I've currently been using is like http://packagingoptionsdirect.com/8-oz-french-square-clear-glass-bottle-028047?gclid=EAIaIQobChMIqMnmme_g2gIVgUSGCh3frw2_EAQYAyABEgKgG_D_BwE one with a rubber stopper and plumbing valve in place to hold vacuum once evacuated, which works well, but I now need something in a 3-4" width but not any larger really (no more than 16 oz size). A first thought is a Mason jar with a suitable rubber stopper for the top, but I don't know if they could attain and hold that sort of vacuum for a month (the French square jars easily do). Budget is limited, otherwise I'd just have a suitable vacuum desiccator chamber. The French square jars come up to 32 oz at good prices, but the mouth still isn't wide enough. Thanks in advance.

Jon

Welcome to the PF, Jon.

We just need to be careful not to allow dangerous discussions here at the PF. We'll see how this discussion goes, and hopefully you can get some good suggestions. Whatever you end up with, it will be important to have a protective barrier around the jar to contain any implosion/explosion fragments if there is a problem. I (unfortunately) have some experience with an exploding glass jar, and it was just pure luck that my roommate and I were not in front of the jar when it exploded.

And even though you are on a budget, for less than $120 you could get a standard Bell Jar that would probably be a lot safer for your experiments...

https://www.zoro.com/sp-scienceware...MI9b-rsrDi2gIVA9bACh2T9A-9EAQYAiABEgJODvD_BwE

 

[joniverson]

Thanks for your fast response. No dangers intended, and perhaps I should have further explained initially.

Last year, I started freeze drying certain insects for preservation and color retention purposes. Some insects, due to their nature, are very hard to preserve well and this includes soft bodied ones like caterpillars. However, based on this article, I was able to fashion together a cheap vacuum apparatus that has done the job nicely.

Page 279 there shows the system I have been using, minus the faucet aspirator (as I use a single stage electric pump). However, being only 8 oz bottles I am limited and cannot advance to larger insects such as spiders, hence the reason for my post. Those particular bottles, being thick walled, have had no trouble retaining vacuum in the freezer for up to 6 weeks.

Plus, as you can see, the bottles are quite inexpensive. I was hoping to find something wide mouthed, in the 3-4" range, and not that much larger that would accommodate the larger insects. I know rubber stoppers can be found in these larger sizes and, with careful searching, can be obtained fairly cheaply.

I looked into the vacuum chambers, such as the one you shared above, but most reviews seem point to the fact that they won't maintain vacuum for more than 24 hours and I need something as described above.

Thanks!

 

[BillTre]

To protect against any implosion, you could put your vacuum chamber in a 5 G plastic bucket with a top with holes drilled in it for the hoses/tubings. The buckets can be obtained from places like Home Depot or Lowes for <$10 usually. They are quite strong.

The kind of glass has an effect on the strength of the container. Pyrex and similar glasses are pretty strong. I have used them for tissue culture media sterile filtration.

You could also get polycarbonate or related plastic (acrylic is kind of brittle in comparison) containers from restaurant supply stores.
Price will vary with size and you are more likely to find something like a straight edge beaker rather than a bottle. They would require a larger plug, but provide a larger opening/volume.

Round is usually stronger than square containers.

I have used vac chambers similar to the one pictured above and they definitely kept the vacuum pretty well. It may be that the seal at the bottle or in the valve need to be re-greased (with vacuum grease ideally) to maintain the vacuum.

If the seal at the bottom is messed up, you can remove it and build a new one with silicon aquarium sealer.
Squirt it in the seal groove, put a thin layer of grease on the top and nestle the top into the goo. Leave along until silicon is set.

I like your project and if I had time, I would probably try it myself.
I haven't read the whole article, so I am wondering: how you maintain your sample in a frozen state? Keep the apparatus in a freezer?
Lucky for me I have a frig/freezer that I have already drilled holes in for similar purposes. Of course a freezer would also provide some protection against an implosion.

How long does it take to freeze dry your insects?
Do you poke holes in the cuticle?
Have you tried anything like flowers?

 

[joniverson]

To protect against any implosion, you could put your vacuum chamber in a 5 G plastic bucket with a top with holes drilled in it for the hoses/tubings. The buckets can be obtained from places like Home Depot or Lowes for <$10 usually. They are quite strong.

Thanks, but the problem is that it sacrifices portability. I need to keep everything frozen from the start, so I would have to remove, apply vacuum, and then return and that's only if it's ok to be outside of the bucket for a month.

The kind of glass has an effect on the strength of the container. Pyrex and similar glasses are pretty strong. I have used them for tissue culture media sterile filtration.

You could also get polycarbonate or related plastic (acrylic is kind of brittle in comparison) containers from restaurant supply stores.
Price will vary with size and you are more likely to find something like a straight edge beaker rather than a bottle. They would require a larger plug, but provide a larger opening/volume.

Round is usually stronger than square containers.

Interesting and I may look into it, thanks. I do know that Mason jars are designed for a certain amount of vacuum and even temperature differences, but I haven't been able to find any published maximum vacuum data. Since most food appears to be vacuumed down to roughly 20" Hg, I suppose I could stop the vacuum process there. It would just take longer for the freeze drying process to complete.

I have used vac chambers similar to the one pictured above and they definitely kept the vacuum pretty well. It may be that the seal at the bottle or in the valve need to be re-greased (with vacuum grease ideally) to maintain the vacuum.

If the seal at the bottom is messed up, you can remove it and build a new one with silicon aquarium sealer.
Squirt it in the seal groove, put a thin layer of grease on the top and nestle the top into the goo. Leave along until silicon is set.

I may go this route if no other way, but I'd just have to be sure I can return the chamber if it won't hold vacuum. The problem lies in keeping the vacuum while in a frozen state over a one to two month period.

I like your project and if I had time, I would probably try it myself.
I haven't read the whole article, so I am wondering: how you maintain your sample in a frozen state? Keep the apparatus in a freezer?
Lucky for me I have a frig/freezer that I have already drilled holes in for similar purposes. Of course a freezer would also provide some protection against an implosion.

How long does it take to freeze dry your insects?
Do you poke holes in the cuticle?
Have you tried anything like flowers?

Basically, it boiled down to desperation. I tried several other methods of caterpillar preservation, but in every case color spoilage would occur in a very short time with the caterpillar either turning black or otherwise severely color fading. Even just alcohol preservation would cause fading, etc in relatively short time.

So, research led me to try the freeze drying method. Initial articles showed promise, but at a significant investment, but a little more research led to the above article. Basically, the insect and drierite desiccant are first sealed and frozen together in a standard freezer for 24 hours. The insect is separated from the desiccant as to not cause deforming of the insect (I use a small piece of balsa wood). Then, vacuum is applied and with the small bottles, I just leave them in the freezer while applying vacuum. With the 8 oz French square bottles, I can attain 27-29" Hg vacuum. The article mentioned that for a 2" size caterpillar, at this level of vacuum, sufficient water loss occurs after two weeks and I found this to be the case as well. You can weigh your specimen both before and after drying to confirm. Best of all, there is no noticeable color spoilage nor any deformities. After two weeks, the bottle is removed from the freezer and nothing is touched for 24 hours to allow everything to reach room temperature. Then, the valve is very slowly opened.

No, I haven't tried anything other than caterpillars, a giant hornet, and stag beetles. The hornet took about the same amount of time, but the stag was left in for a month. I don't see why it wouldn't work for flowers, but it seems many people have had great success with burying flowers in desiccant and then either microwaving them or placing into the oven. I tried something similar with a caterpillar and it was just ruined.

Note that it's quite possible to just place an insect inside a closed jar with desiccant and leave at atmospheric pressure inside the freezer, but the freeze drying process takes much longer, roughly 100 days for a standard sized caterpillar so, if you don't mind the wait, that would be the safest route.

 

[BillTre]

a giant hornet, and stag beetles

Cool.
You know what kind?
One year, when I was a kid, there was a bunch of cicada killers under my back porch.

 

[joniverson]

Sure, the hornet is the European hornet (Vespa crabro) and the reddish brown stag (Lucanus capreolus). I have plenty of cicada killers too, but I haven't yet tried freeze drying them.

 

[berkeman]

I don't know if this helps, but if you start with a standard Mason Jar like in the picture below, one of the issues is the strength of the flat lid against the vacuum pressure force. You might be able to craft a single support pillar in the middle of the jar to brace the lid against excessive bowing inwards.

You would need to drill a hole and mount a hose nipple in the lid, but I've done something similar for my brake bleeder setup. The pillar would restrict the volume a bit for your larger spiders, but maybe it could be made to work.

I still would recommend integrating a plastic overall enclosure for implosion protection, maybe smaller than the bucket and more easily portable to put into your freezer. I just don't trust bare jars with potential explosion/implosion hazard issues.

 

[joniverson]

I don't know if this helps, but if you start with a standard Mason Jar like in the picture below, one of the issues is the strength of the flat lid against the vacuum pressure force. You might be able to craft a single support pillar in the middle of the jar to brace the lid against excessive bowing inwards.

I actually have some rubber stoppers on the way that I think will fit the jars. #12 and/or #13 for standard mouth and #14 for wide. I plan on drilling 1/4" holes in the center for the tubing like with the square jar stoppers I already use. The big uncertainty is how much stoppers of this size will bow under pressure.

You would need to drill a hole and mount a hose nipple in the lid, but I've done something similar for my brake bleeder setup. The pillar would restrict the volume a bit for your larger spiders, but maybe it could be made to work.

It's possible that I may still need to do this with the stoppers, not sure.

I still would recommend integrating a plastic overall enclosure for implosion protection, maybe smaller than the bucket and more easily portable to put into your freezer. I just don't trust bare jars with potential explosion/implosion hazard issues.

I have some spare containers similar to https://www.containerstore.com/s/kitchen/food-storage/canisters/hermetic-acrylic-canisters/123d?productId=10018773&country=US&currency=USD&utm_source=tcscompshop&utm_medium=feed&utm_campaign=google&cid=cse:PLA&gclid=EAIaIQobChMI0tv1obvk2gIVgx6GCh3vrwMQEAQYBSABEgJSzvD_BwE that might work. I could poke a hole in the top/ side to make room for the vacuum tubing.

 

[jim mcnamara]

A looong time ago, a graduate student and several of us other non-experts, set up and lyophilized a North American beaver - Castor canadensis, a 24kg male that died at the Washington National zoo's farm. I had tried it on small plant specimens.

If it is of any consequence his name was Chucky. After removal of internal organs and taxidermy help, freeze drying took about 4 months and a very high vacuum in a special large metal container, shaped like a diving bell, with a round door. Chucky used to reside under plexiglass at the Smithsonian Research Annex in Lanham, Md. Don't know his whereabouts now.

The point was: it became increasingly expensive, problematic, and time consuming the bigger the specimen was to freeze dry it. It seemed to me to be more of an art. At the outset, there was lots of guesswork, vacuum pump problems, and temperature problems in the chamber which had to be set correctly. A freeze dryer requires a temperature differential between the specimen’s eutectic temperature and the freeze dryer collector. And later on, a very slow temperature increase to allow "bound" moisture to be extracted. I am pretty sure she had minimal guidance for what she was really doing, she just got lucky. I knew nothing helpful, but I learned:

Lyophilization is very practical mostly for preserving microbiological products and small items. The museum's dream of production lyophilization for large moose-sized animals faded quickly after Chucky.

It is still done often on smaller specimens and food products:
https://www.cuddonfreezedry.com/applications/

Although people have their deceased pets freeze dried, there is a limit to the size of pet.
http://abcnews.go.com/US/grieving-pet-owners-opt-stuffing-freezing-drying-deceased/story?id=16022869

So, you should probably restrict your dreams to large bugs and centipedes

 

[jim mcnamara]

This site has small freeze dried animals for sale, which still seems to be the practical limit:
http://allcrittersandpetsfreezedry.com/critters-sale/

 

[joniverson]

Very nice! The good news is that those animals are significantly larger than I will ever go and I wouldn't even want to attempt that unless I had a way better vacuum system. Actually, about the largest I'm looking at will be garden spider size. If not for the leg span of those, I probably wouldn't have had to move beyond my 8 oz square bottles.

Another area I'm interested in is plastic embedding of insects. There is very little web information available concerning this, but I found an excellent, albeit quite aged but still significant resource that I intend to use should I ever decide to try it. The biggest issues with plastic preservation are remaining specimen moisture content and yellowing of the plastic. Moisture can be a huge problem, but the book has discussion of techniques tackling this issue that I have not read anywhere else. The author was able to preserve not only critters, but horseshoe crabs, a pig fetus, and similar. A must read, but I must warn that liquid plastic used in the quantities discussed will be expensive, especially after one or more failures.

 

[Tom.G]

Here is proof-of-concept that a 1-½ quart canning jar is good for 25in Hg of vacuum. That's all my cheap vacuum pump was good for, in fact I had to mostly fill the jar with water to get the volume low enough for that vacuum. The little dome in the middle of the lid operates around 10in Hg. The second port on the jar has a vinyl dip tube which I doubled over and held crimped shut with a Binder Clip from the Stationery store.

As you can see, the experiment was done in the kitchen sink, with a heavy leather motorcycle jacket as a blast shield. Since it didn't blast, the jacket was removed and the photo snapped.

I would be a little concerned with using a rubber stopper in a wide mouth jar. It seems to me you would get a wedge effect of the stopper around the rim of the jar. Could the wedge effect be enough to but tension on the jar rather than compression?

Cheers,
Tom

 

[joniverson]

Thanks for sharing, Tom. I'm not surprised you got it down to 25" and holding up as the Foodsaver and other pumps bring it down to 20.

I've decided that I'm going to place whatever jar is used inside of the plastic hermetic canisters I mentioned before. Poke a small hole in the side or top so the tubing will reach the mason jar, and go from there.

If I could ask, how do you have your ports in place... glued or soldered? I was thinking of that, but not sure how long the seals would hold for the 2-4 weeks it would be frozen. Thanks.

 

[WarrenE]

Here in the lab we use lyophilization flasks for such things: https://us.vwr.com/store/catalog/product.jsp?catalog_number=10148-032

If too expensive, try Amazon. Bel-Art may also have something cheaper. These flasks are wide mouthed and designed for vacuum. Hope this helps.

 

[joniverson]

Although I'm planning on the mason jar inside of plastic canister method, I checked out the lyophilization flasks. Unless I'm wrong, these seem to be 100% borosilicate glass with no lip, so I'm wondering if standard, wide mouthed borosilicate jars might do the trick. Of course, I might be missing something like special treatments and so forth, but an interesting thought.

 

[joniverson]

#12 and #13 stoppers arrived today, they were drilled and 1/4" copper pipe and valves installed. I then placed each stopper on a standard mouth Mason jar. I don't yet have the plastic canisters, so the jars were placed some distance away and then vacuumed down to 29" Hg. They seemed to hold fine and the valves were closed. Will recheck vacuum in a day or two. Both stoppers fit the jars. #12 was actually a better fit and #13 just inside the jar rim. Will report back.

 

[Tom.G]

how do you have your ports in place... glued or soldered?

Soldered. The lid will flex in use, breaking any glued interface. Use a sharp knife and a wire brush to get down to bare metal. Then I used a propane torch (a large solder iron would work too) and Silver Solder to solder brass hose barbs into drilled holes. Tin both lid surfaces and the brass fittings before assembly, that way you need less heat on the lid. I don't recall for sure, but I may have had wet paper towels on the gasket to avoid destroying it. You want a solder fillet on both lid surfaces. Plan ahead. My first attempt had the brass fittings pointing away from each other; couldn't get the band on the lid. I haven't found any Silver Solder with flux in it so you will need some flux too. Clean all the flux off afterwards as most of it is corrosive and hygroscopic. A stiff toothbrush and ordinary rubbing alcohol works if you get to it as soon as it cools from soldering. If you don't have some experience soldering this way, perhaps you can find someone that does. You don't want any pinholes in the solder joints. The again, lids usually come in multi-packs so you can get lots of practice if you want to.

If the lid doesn't seal well enough for long-term storage, use vacuum grease (or maybe silicone grease) on the gasket.

Keep us posted on your progress.

Cheers,
Tom

 

[Baluncore]

The difference between a perfect vacuum and half an atmosphere is only a factor of two. Any rubber ring sealed preserving jar should withstand a perfect vacuum without a problem. It is important that your vacuum jar cannot be pressurised. Positive pressures are a danger because energy stored in a compressed gas can be increased without limit to explosive destruction. Bell jars are safe because they seat on a flat surface, so can only support a pressure reduction, which is obviously limited by atmospheric pressure.

When preserving food in a full vacuum jar, the hot material cools and so the pressure reduction may be limited initially only by the vapour pressure of the materials contained. Any biological activity that produces gas to a positive pressure will break or pop the seal safely.

The very real fear of vacuum implosions originates from large empty thin wall containers such as CRTs. When the neck of a CRT fails, the electron gun at the back end of the tube can accelerate towards the centre of the screen. Early RADAR tubes in aircraft during WW2 had no external ballistic protective screen. The electron gun could punch a hole through the screen, then injure or kill the operator with a guaranteed head shot.

The danger of vacuum containers comes from the lack of a solid or liquid content that will limit the trajectory of implosion fragments. Where the vacuum space is small there is no real danger. An insect has insufficient bulk to intercept glass fragments so you need to use a thick walled preserving jar with a vacuum sealed lid.

As the insect or sample dries, any water vapour released will need to be removed from the container. That can be done by repeated use of a vacuum pump, or the water can be chemically absorbed. If water is not removed, the pressure will rise and the freeze drying process may be interrupted.

Edit: An example of an implosive vacuum accident was the sympathetic cascade implosion of 6,600 photo-multiplier tubes in the first Super-Kamiokande neutrino detector in 2001.

 

[NTL2009]

...

The danger of vacuum containers comes from the lack of a solid or liquid content that will limit the trajectory of implosion fragments. Where the vacuum space is small there is no real danger. An insect has insufficient bulk to intercept glass fragments so you need to use a thick walled preserving jar with a vacuum sealed lid.

As the insect or sample dries, any water vapour released will need to be removed from the container. That can be done by repeated use of a vacuum pump, or the water can be chemically absorbed. If water is not removed, the pressure will rise and the freeze drying process may be interrupted.

Very interesting and informative post. I knew implosion of a CRT was dangerous, but had never heard of those specifics of WWII radar implosions accelerating the electron gun and injuring the operator. Gruesome!

So it would seem that for the OP's case, adding as much desiccant as possible to the jar would be beneficial in several ways. Less volume of air to remove (easier on the pump), less stored energy (safer), and you want the desiccant anyway to help dry the specimen.

 

[Baluncore]

So it would seem that for the OP's case, adding as much desiccant as possible to the jar would be beneficial in several ways.

True.
Also, if a stitched cloth bag containing the desiccant was made, one that covered the sides and possibly also the bottom of the glass jar, it would limit the free path of fragments during an implosion. It would perform like a defensive sand bag, that would limit fragment ejection and velocity.

I am seeing a long thin sausage bag of desiccant, wound as a helix and stitched across between turns. It would not need to give a total 100% coverage, but could be double spaced, sufficient to give a view of the contents.

Maybe use contact cement to glue the sausage in a spaced helix to the inside wall of the glass jar.

 

[joniverson]

Each jar will have roughly 1/3 total jar volume of desiccant (drierite) added to the bottom, in accordance with the article, along with a separation screen between the desiccant and insect. With the caterpillars I dried last year, they took just one week since I had substituted a single stage pump for the faucet aspirator mentioned in the article.

For protection, I'm considering either a plastic canister surrounding the Mason jar and/or taping the jar, but if the latter is used I need to be able to see what's happening within the jar.

The final rubber stopper arrived today and it is large enough to cover a wide mouth Mason jar. One quick question: is it possible to apply high vacuum grease around the stopper edge? I think I read somewhere that the grease was not to be used on certain rubbers, but not sure.

 

[Baluncore]

The type of rubber will determine the grease. I would try petroleum jelly with a synthetic rubber seal, but a vegetable oil with natural rubber. Only a very thin film of sealant will be needed on the rubber seal. The pressure reduction will probably never be sufficient to justify vacuum oil.

The stopper should seat on the end and/or the outside of the jar. The vacuum will be compressing the walls of the jar, an internal stopper would wedge the jar open at one end, which will more than double the stress near the neck of the jar. It is much easier to seal a vacuum with an external cap than with an internal plug. An internal stopper will be difficult to extract once it has shrunk and been drawn into the neck of a jar.

The pressed sheet metal caps for preserving jars will be easy to modify with a bulkhead fitting to the vacuum system. You might also consider a reversed bicycle valve in that position.

Have you looked at the way a single flat rubber washer is compressed, or an O-ring is rolled to seal a preserving jar?
https://en.wikipedia.org/wiki/Mason_jar
Fowler's Vacola jars tend to have wider necks than some others.
https://en.wikipedia.org/wiki/Fowler's_Vacola

 

[rbelli1]

When preserving food in a full vacuum jar, the hot material cools and so the pressure reduction may be limited initially only by the vapour pressure of the materials contained.

The vapor pressure of water is only a couple of percent atmosphere at room temperature. When doing normal canning especially with a pressure cooker the final vacuum should be nearly zero.

Two questions:
1) Am I making some sort of mistake here?
2) Is that last two percent that much of a difference from essentially perfectly safe to "RUN FOR YOUR LIVES!"

BoB

 

[Baluncore]

1) Am I making some sort of mistake here?

No mistake that I can see. If you can cap the jar without it falling apart then it should safely hold a perfect vacuum, possibly even if it has a crack in the glass.

There can never be more than one atmosphere of negative pressure, so preserving jars are very safe. Positive pressures must be avoided, but the cap and seal are designed to prevent positive pressures. Any other container will need to be carefully assessed.

2) Is that last two percent that much of a difference from essentially perfectly safe to "RUN FOR YOUR LIVES!"

No. The last two percent to a perfect vacuum are insignificant and quite safe. On the other hand, the last two percent with positive pressure will be as deadly as the last 0.1% because that is when the glass will shatter explosively due to the high internal pressure.

Vacuum is inherently safe so long as you are not in it for long, and you do not stand at the end of a shock tube gun barrel. Air pressure on the other hand can be deadly with only a couple of psi, which is your internal pressure, and getting air under your skin can cause an air embolism with symptoms like the "bends". You should be able to suck a vacuum with your mouth down by 10 psi to about 4 psi absolute. You will not be able to blow 2 psi positive without embolism, probably of your salivary ducts initially, maybe followed by a stroke, depending on where the bubbles go.

 

[arydberg]

I suggest you try vacuum food storage containers as in the below link. They are plastic so the risk is smaller. I am assuming they will hold the vacuum.

https://www.houzz.com/photos/contemporary/kitchen-canisters-and-jars/pid=46594324

 

[Nik_2213]

There's a heavy duty plastic mesh-sleeve made for protecting and containing lab glassware. Comes in different diameters. We used it on glass rotary evaporator condensers etc. Also made for a fair grip on round and pear-shaped flasks, which were so slippery when wet...

That Vac dessicator pic reminds me of when some-one put a red-hot crucible into a too-small *ordinary* dessicator to cool. The lid 'hovercrafted' across and clamped shut. Too tight to slide. We needed the data. We'd settle for the crucible. Smashing the glass dessicator was not a favoured option.

I figured a fix: I put a rubber band around the join, put the small dessicator inside our carefully emptied largest vacuum dessicator then, very slowly, pumped it down. Ta-da ! Lid lifted, rubber band prevented a re-seal, slowly vent to atmospheric, job done.
;-))

 

[jim hardy]

If you don't need to see through it, ...

seems to me this type of product already handles vacuum...

not really cheap, though. Thrift shop perhaps?

old jim

 

[Nik_2213]

No, it only handles the vacuum between the double skins. IIRC, there's a foam spacer to stabilize them.

Can you get hold of some flanged or threaded 'heating' pipe about 4 in (100mm) ID ? Blanking plates etc allow connections to be screwed in...

Hmm. How did the classic 'Scientific American' amateur scientist articles handle this ?

 

[jim hardy]

No, it only handles the vacuum between the double skins.

My thought was that evacuating it places zero differential across the inside chamber skin . So even using a glass lined one doesn't invite implosion.

 

[arydberg]

I suggest you try vacuum food storage containers as in the below link. They are plastic so the risk is smaller. I am assuming they will hold the vacuum.

https://www.houzz.com/photos/contemporary/kitchen-canisters-and-jars/pid=46594324

I have one of these. The wall thickness is between 3/8 and 1/2 inch which makes it possible to drill & tap fro a pipe thread.

 

[Baluncore]

I have one of these. The wall thickness is between 3/8 and 1/2 inch which makes it possible to drill & tap fro a pipe thread.

What pressure reduction can you achieve with the green button pump built into the lid?
If the pump works, why do you need to drill the plastic container wall?

 

[joniverson]

Since it will be nearly a month before the insects I desire are collectible, today I ordered some vacuum gauges similar to but less costly like these. I have two options for use: 1) either fashion a quick connect/ disconnect system like used for air compressors to only occasionally check on jar vacuum while in the freezer, or 2) use a 1/4" female threaded "t" adapter and keep the gauges on permanently while frozen. I actually prefer #2. According to specs, they should work at freezer temperatures, but I was hoping to confirm if anyone has done it successfully? Thanks.

 

[Nik_2213]

Slightly off topic, but this may be of interest for preserving super-fine detail...
https://phys.org/news/2018-05-magnetic-fields-disrupt-ice-nucleation.html

 

[arydberg]

What pressure reduction can you achieve with the green button pump built into the lid?
If the pump works, why do you need to drill the plastic container wall?

the green button is not a pump. Unless you release the vacuum the jar is impossible to open. The function of the green button is to release the vacum. My idea is to fit a vacuum hose to a barbed fitting with a pipe thread and thread the fitting on to the vacuum jar as i only have the container and do not have the pump but i have another vacuum pump.

 

[Baluncore]

The function of the green button is to release the vacum.

Is the big green lump in the middle a handle for the lid or the vacuum release?
What is the much smaller green button in one corner?

Is there a vacuum storage container with an integral pump, or only external?

 

[joniverson]

Hello everyone,

I wasn't sure whether or not to start a new thread, or continue this one. Please reread my post #4 above to get an idea of what I have been trying to do.

The idea has been to freeze dry soft bodied insects for preservation. This would include caterpillars, spiders, soft beetles and similar. I initially started with basically a homemade vacuum system using heavy walled 8 oz jars fitted with rubber stoppers and the stoppers drilled to accept plumbing valves to allow vacuum to be maintained after the jar is evacuated by single stage pump (post 4). While this system has worked out nicely, I've been needing to go with something larger. My latest experiment was using mason jars. While I can easily seal the jars this way, and they maintain vacuum well, there doesn't seem to be a reliable way to release the vacuum slowly when the time has come to remove the insect (which generally occurs after being under vacuum for two weeks in the freezer).

After careful saving, budget finally allowed me to obtain one of these, which arrived two days ago. To my disappointment however, this device is not holding vacuum. I applied Dow high vacuum grease to all joints and both sides of the rubber ring at the halfway point of the container sections, but after a few hours in the freezer, I am losing vacuum. I will point out that, in the original article, the author says to NOT grease the rubber ring/ gasket. Not sure why. Can anyone shed some light as to why I am losing vacuum? Is there any way to tell where exactly the leaks are occurring?

 

[BillTre]

The original article is old. Your device is new.
I would see what the manufacturer of the desiccator you bought says about the issue.
They may also have something like a FAQ or help line where you might get some idea about why it isn't working.
If not the seals, it may have something to do with the valve.
If the manufacturers help doesn't help, there might be appropriate to return it for a replacement.

 

[joniverson]

I would see what the manufacturer of the desiccator you bought says about the issue.
They may also have something like a FAQ or help line where you might get some idea about why it isn't working.
If not the seals, it may have something to do with the valve.

Here is what the manufacturer says, so I am right in using the grease. I also swapped out valves for a different one, still getting loss. Any way to tell where the leak may be coming from? Can I take the unit from the freezer and tip it in a tub of water?

 

[BillTre]

I could not find any directly useful information on the manufacturer's site, but I did see a different view of the desiccator.

The valve is on slip fitting with the dome. It should slip on and off. It could be leaking and should be greased up (unless you already did).
If that doesn't work, I would disassemble the valve, grease the contacting surfaces, and reassemble.
Sometimes just taking something apart and putting it back together can fix it (dust falls out or ring sits properly).

If that doesn't work go to the company you bought it from and tell they you are disgruntled and want some decent information on a product you bought from them. But do it in a friendly way.
They might be able to provide a useful contact at the manufacturer.

 

[BillTre]

The sealing issue is not in their FAQs, which are few.
You could send a message to the manufacturer here, asking about your problem.
I would do this first if you can't figure out the problem yourself (which is always better).

 

[BillTre]

They have a tech manual here. Its mostly about properties of the materials their various products are made of.
Not useful for advice, but among many other things, it will list the resistances to solvents of different plastics. Figure out what your item is made of, look it up, and know what not to expose it to.
It is also a good way to know what products to look for if you want to use particular chemicals.

According to the items webpage it is made of PP/PC; probably polypropylene and polycarbonate parts. These are plastics that can take temperatures high enough to autoclave them (common lab sterilization method (you can do it in a pressure cooker!)). However, they might warp, making them more difficult to use.

 

[joniverson]

Thanks, BillTre, but all may not be lost yet. I just made one discovery which could be causing reading errors. When I placed the desiccator in the freezer after vacuuming, I also placed a simple oil-filled gauge in on top of the removable tray. This internal gauge began to register vacuum drop from about 28 down to 22" Hg over the course of three hours while in the freezer. However, a separate gauge at room temperature coupled to the desiccator valve shows the original 28" Hg. Therefore, the internal gauge might be in error from the cold. Perhaps the oil contracted or even started solidifying thereby affecting the needle. When I bought the gauge, the ambient temp was supposed to be down to -4 F (according to the specs listed at that website). With my freezer bottoming out at around 1 F, it should work but maybe not. I'm going to let the desiccator continue undisturbed in the freezer until tomorrow and see if vacuum changed any on the external gauge before I go any further.

 

[Tom.G]

Their tech manual shows the minimum temperature for PP (polypropylene) as -10°C (14°F).
Also check the chemical compatibility table.
But I agree that the oil filled gauge is most likely the problem of the moment.

Edit 1: You might want to check the temperature rating of the guage.

Edit 2: A gauge is oil filled to increase mechanical damping of the needle. Not needed here as the measurand (chamber pressure) is essentially static. Try a gauge based on an Aneroid Barometer:
https://www.britannica.com/science/atmospheric-pressure#ref128230
http://marinegyaan.com/what-is-aneroid-barometer-its-principle-and-correction/

Cheers,
Tom

 

[joniverson]

Thanks for the replies, guys. BillTre and Tom G, you both seem pretty thorough, something I should have been before using the device as intended. However, after roughly 64 hours in the freezer under vacuum, I tested it today using the external gauge and the good news is that there has been very little, if any, change in vacuum (perhaps 0.5" Hg change but not even sure of that). When I was having vacuum retention problems (or just thought I was), one of the first things I did was change out the original flimsy and press-to-fit valve for one of my copper ones I use for my thick walled jars. I had to epoxy a copper tube in place and then coupled the new valve to the tubing with lab vacuum tubing. I was a bit worried about outgassing from the epoxy (JB Weld), but I read it wasn't an issue unless much greater vacuums were used. The plumbing valves can sometimes leak, so I wanted to be sure it was easily replaceable.

This new chamber with valve seems to be holding vacuum better than my thick walled jars with stoppers. I usually have to re-evacuate the latter once or twice a week due to some vacuum loss, but the chamber would not have needed an additional vacuuming so far. So, for now, I consider it ready for use and next week it will have some matter placed within it.

Thanks again for the help and suggestions. Oh, I will be removing the gauge I dropped in there as it will not register properly, but it will be no issue coupling a room temperature gauge as I do with my jars.

 

[joniverson]

After nearly two weeks in the freezer, the vacuum in the chamber has not changed. I now feel confident using it for future projects. I did remove it from the freezer a day ago and the vacuum gauge I placed within it read correct levels once it warmed up. Apparently, the gauges are affected by the cold, so I'll know not to place it within the chamber in the future.

Thanks again for all those helpful suggestions and comments.

 

[dlgoff]

Thanks again for all those helpful suggestions and comments.

I want to thank you for letting us know how it turned out. Nicely done thread, IMO.

 

[mp3car]

It is still done often on smaller specimens and food products:
https://www.cuddonfreezedry.com/applications/

Although people have their deceased pets freeze dried, there is a limit to the size of pet.
http://abcnews.go.com/US/grieving-pet-owners-opt-stuffing-freezing-drying-deceased/story?id=16022869

So, you should probably restrict your dreams to large bugs and centipedes

I believe this was performed on people by a group of scientists in China, they did it to humans and it became a museum exhibit that toured around the US under a cloud of suspicion that the subjects used were tortured/executed political prisoners…. Anyone else remember that, or get a chance to see the exhibit? P.s. Sorry for resurrecting an old thread….

 

[berkeman]

I believe this was performed on people by a group of scientists in China, they did it to humans and it became a museum exhibit that toured around the US under a cloud of suspicion that the subjects used were tortured/executed political prisoners…. Anyone else remember that, or get a chance to see the exhibit? P.s. Sorry for resurrecting an old thread….

I saw that exhibition about 15 years ago when it came to San Jose here in Silicon Valley. Pretty weird stuff. It looks like it may have had a couple different names:

Real Bodies: The Exhibition https://www.dailymail.co.uk/news/ar...adavers-come-Chinese-political-prisoners.html

BODY WORLDS https://www.google.com/url?sa=t&rct...usg=AOvVaw3qNe09vA4FDobD7CEY8wPe&opi=89978449