I How to flatten the surface of a viscous gel?

[guyburns]

I have gel which has a specific gravity of about 0.8 and a stated viscosity of 25000 mm²/S (whatever that means). It's thicker than honey. It just sits there with an uneven top surface.

About 20cc are in a container and I want to flatten the surface. The best I can do is to shake the container horizontally a few times in one direction, rotate 1/4 turn, shake again, and so on. Do that for several revolutions, tap it on the table a few times, and the surface is reasonably flat.

I happen to have a 240 Volt transformer that vibrates (see attachment). It has a right-angled metal arm that is attached externally, about 3mm thick, separate from the core but obviously is part of the magnetic circuit. When you apply power, the arm moves 1-2mm at 50 Hz. The device I got it from had a diode that could also be put in circuit with a switch, thus operating the thing at 25Hz -- and a larger, much noiser vibration.

Anyway, I made up a rig, put the container on top of this transformer thing, and in terms of surface flattening, nothing happened even after 30 minutes.

So two questions.

Q1: What is that type of transformer called? I have been unable to find any advertised for sale.

Q2: What automatic method could I use to flatten the surface? My manual shaking method, about 3 Hz, and then solid bumping, works pretty well, but is it possible to determine the optimum frequency such shaking should be applied at?

I did have another idea (not implemented): use something like a windscreen wiper motor running at 2-3 Hz, and hang the container from the extended arm that normally drives the wipers. The container would be moved up and down, experiencing forces at the top and bottom of the cycle, and maybe the surface would be flattened -- if I knew the optimum frequency and range of movement.

Thanks in advance for any suggestions.

 

[Chestermiller]

Is it really a gel, which won't deform below some specific shear stress, or is it a liquid all the way down to zero shear stress?

That viscosity is about 3x the viscosity of typical honey.

Are you able to spread the fluid by direct contact, such as with a brush?

 

[Baluncore]

Thanks in advance for any suggestions.

You could heat the surface with a flat iron, it might melt, then set flat.

 

[Lnewqban]

Do you have access to a lab centrifuge to perform a test?

Please, see:
https://www.scimetricsinc.com/categ...y-centrifuge-with-8x15ml-rotor-up-to-3500rpm/

 

[guyburns]

Thanks for the suggestions.

* It's a gel. It doesn't move unless prompted.
* The brush idea sounds good. I'll give it a go.
* I know that heating won't work. It's not going to melt.
* Centrifuge – I haven't got access.

I've started reading up on mixing (flattening in my case) viscous materials. Turns out it is a difficult thing to do. Might have to stick with shaking and tapping.

 

[Lnewqban]

If you find a way to keep the sample fixed in a horizontal position inside the centrifuge of a washing machine, it may work for experimentation.
If the centrifugal effect proves that it can replace the shake and tap, then you can engineer a more permanent solution.

 

[guyburns]

I like the washing machine idea. I'll see what I can come up with.
I had thought of somehow using my old turntable set to 78RPM, but I don't suppose that's fast enough.

 

[zipmechanic]

When testing with vibration, was the vibration from the device properly transferred to the gel? If you put the container of gel on top of the vibrator, likely the vibration is not being transferred to the gel due to small gaps in contact between the container and the vibrator.

I would highly recommend getting a vibrating wand (use your imagination here) of some form, and submerging it into the gel. This works very well for levelling highly viscous compounds in other industries (for example concrete).