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

  1. Apr 29, 2018 #1
    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 this 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.

  2. jcsd
  3. Apr 29, 2018 #2


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  4. Apr 30, 2018 #3


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    Thread reopened provisionally.
    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...


    Last edited: Apr 30, 2018
  5. Apr 30, 2018 #4
    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.

  6. Apr 30, 2018 #5


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    To protect against any implosion, you could put your vaccuum 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?
  7. Apr 30, 2018 #6
    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.

    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 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.

    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.
  8. Apr 30, 2018 #7


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    You know what kind?
    One year, when I was a kid, there was a bunch of cicada killers under my back porch.
  9. Apr 30, 2018 #8
    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.
  10. Apr 30, 2018 #9


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    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.

    Mason Jar.jpg
    Last edited: Apr 30, 2018
  11. May 1, 2018 #10
    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.

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

    I have some spare containers similar to these that might work. I could poke a hole in the top/ side to make room for the vacuum tubing.
  12. May 1, 2018 #11

    jim mcnamara

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    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:

    Although people have their deceased pets freeze dried, there is a limit to the size of pet.

    So, you should probably restrict your dreams to large bugs and centipedes
  13. May 1, 2018 #12

    jim mcnamara

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  14. May 1, 2018 #13
    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.
  15. May 1, 2018 #14


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    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?

    Vacuum Mason Jar-1.JPG

    Last edited: May 1, 2018
  16. May 2, 2018 #15
    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.
  17. May 2, 2018 #16
  18. May 3, 2018 #17
    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.
  19. May 3, 2018 #18
    #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.
  20. May 3, 2018 #19


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    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.

  21. May 5, 2018 #20


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    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.
    Last edited: May 5, 2018
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