how to stop a powder from clumping and clogging a dispenser in a wet enviroment
August 21, 2007 7:29 PM   Subscribe

how do I dispense a very hygroscopic powder in a very moist environment without causing clumping in the remaining powder and without clogging the dispenser?

I have what is called a "unit bath". This means that the sink, mirror, shower, and bath are all in one enclosed waterproof room. I shave while I am taking a shower. I use powdered shaving soap to make lather. I have been keeping the powdered soap in a talcum powder squeeze bottle but even with the top slid in the closed position the very hygroscopic power clumps and becomes impossible to dispense after about a week of use. I have tried only keeping a weeks worth of powder in the dispenser but the wall of the container becomes gummy and cleaning it is very time consuming. what would be the best way to dispense the powder and still be able to store it in the shower? container ideas?
posted by Infernarl to Science & Nature (15 answers total)
Is the powder soluble in a highly volatile solvent or propellant? I'm thinking of spray deodorant, for example.

Perhaps your mechanism could flush the dispenser with solvent or propellant after usage.

Another approach used in the food industry is high frequency vibration, to shake clumps loose.

In devices which dispense powdered medication, I think PTFE (Teflon) can be used as a "lubricant", which reduces friction on which powder can clump and accumulate.
posted by Blazecock Pileon at 8:03 PM on August 21, 2007

As an advantage, PTFE is highly hydrophobic, so water molecules don't accumulate on the surface (think of water on a non-stick pan).
posted by Blazecock Pileon at 8:06 PM on August 21, 2007

It may be simpler to switch to shaving soap in cake form along with a brush to help make the lather.
posted by exogenous at 8:10 PM on August 21, 2007

Maybe putting a desiccant in the dispenser would help, e.g. some packets of silica gel?
posted by greatgefilte at 8:16 PM on August 21, 2007

Keep the talcum powder squeeze bottle in a sealable plastic bag with desiccant packs taped to the inside of the bag. Open the bag only slightly to dispense through the opening, and quickly reseal.
posted by Mapes at 8:24 PM on August 21, 2007

Keep the talcum powder squeeze bottle in a sealable plastic bag with desiccant packs taped to the inside of the bag. Open the bag only slightly to dispense through the opening, and quickly reseal.

Maybe. The problem is that you can never allow the squeeze bottle to "inhale" in moist air after you've let it "exhale" to get the soap out of it, or you've allowed moisture/water into the bottle and the soap powder will clump.

Sounds like cake soap is going to be your only option.
posted by SpecialK at 9:50 PM on August 21, 2007

This is a situation in which most people would switch to shave gel.

You could dispense the powder into your hand (or a small dish/bowl?) before entering the shower, thus only exposing an amount you're planning on using to water at a time, and not the whole bottle.
posted by jesirose at 9:52 PM on August 21, 2007

Or, you could keep your powder in a completely open-topped jar, and just let it clump and turn into a cake. A wet brush should pick up enough from the top of that cake to give you a lather.
posted by flabdablet at 10:42 PM on August 21, 2007

Seems like the timing is another variable here.

I'm imagining that the powder only becomes clumped due to the extra moisture in the air when you take a shower, yes? Not due to the normal moisture in the air. If so, just keep the powder bottle in the bag that Mapes suggests and dispense it before you start your shower. Then reseal the bag. That way the open container and the steam never need to co-exist.

Alternately, continue your weekly rationing idea, but use a number of disposable bottles so you don't have to clean them each week. The logical end to this train of thought is single serve containers like powdered coffee creamer.

Finally, since the water vapor seems to be at the heart of the problem, consider bathing options that generate less vapor. Cold showers or baths for instance.
posted by Jeff Howard at 11:48 PM on August 21, 2007

You could try keeping grains of uncooked rice in the talc dispenser with the powder to soak up excess moisture like they do in the south with salt shakers.
posted by BrotherCaine at 2:10 AM on August 22, 2007

Seconding the rice. A cheap, non-toxic desicant that is easy to replace. We use it in both our sugar and salt in the summer when the humidity starts to cause clumping and it works very well.
posted by LunaticFringe at 4:47 AM on August 22, 2007

I will try the silica. I don't want to switch to cake soap (you would know why if you have ever tried Kao shaving powder soap). single serving is also a really good idea. I should collect some coffee creamers and replace the contents. Is silica gel toxic on skin? I had an idea to use something like this crank cereal dispenser but I would probably have to make it myself.
posted by Infernarl at 6:25 AM on August 22, 2007

Keep in mind that unrefined silica gel is sand, so use packets rather than loose gel. Silca gel can be recycled by baking it above 100C. We use a 160 C bakeout for 8 hours in the lab.

Rice is a good idea, but only if starch is more hydrosopic than the soap. It may not be! You'll have to try it and see.

You don't need to put the material in the tube with the soap. You can fill a small jar with your dessicant and put your tube of soap in that, sealing the jar when not in use. An older lever-lock jam jar would work quite well, for example.
posted by bonehead at 7:57 AM on August 22, 2007

Silica gel is chemically identical to quartz, and isn't even a little bit poisonous. Its toxicity is physical.

If you ingest dry silical gel, the granules suck all the moisture out of whatever mucous membrane they touch first, then stick to it, then keep sucking water out until (a) they're saturated (b) the mucous membrane is damaged by rapid dehydration at the contact point.

If you get silica gel pellets on your skin in the shower, the shower water will saturate them almost instantly, rendering them completely harmless.

The coloured moisture indicator pellets that come in some kinds of silica gel may be poisonous; I don't know.
posted by flabdablet at 8:27 AM on August 22, 2007

Silica gel (slicon dioxide) isn't a great dessicant, but it has the advantages of being fairly inocuous and cheap. The coloured inidcator pelets aren't silica gel.

The dessicants are usually other minerals, including calcium sulphate and zeolites among others. The coloured indicators are transition metal complexes, containing cobalt typically. The indicators are almost always sort of poisonous, but don't cause huge problems for skin contact, only injestion. Still, not generally recommended for home use.

Stick with the sachets of silica gel.
posted by bonehead at 9:20 AM on August 22, 2007

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