Getting sticky powder through a small funnel

November 24, 2020 11:36 AM

I need to fill many many small glass bottles with a fluffy, sticky powder. The neck of the bottles is so small i need to use a funnel, but the powder sticks to the funnel, and needs to be stirred in by hand with a stick to fall through. It's messy and taking forever. Any tips to make this easier?

The powder in question gets very sticky as soon as it's in contact with air (I'm guessing the moisture in the air).
It clings to the walls of the funnel.
I need to fill thousands of those bottles so I'm looking to make this more efficient, or even slightly less painful.

I'm thinking of devices like old-fashioned coffee grinders or potato mashers that have a handle that you turn to push the product down through the sieve or grinder. Something like this but very small, i could hack on to the funnel? Does such a thing exist?

I'm all ears if you have any other ideas that might help.

For the curious out there, the powder is Ammonium iron(lll) citrate which is used for making cyanotypes.

posted by PardonMyFrench to Technology (24 answers total)

Does the powder stick to paper as badly as it sticks to the funnels? You might try a paper cone. There is another thread today about conditioner and people have suggested piping bags (most baggies will work) and syringes. Those are both worth a try, too.
posted by soelo at 11:40 AM on November 24, 2020 [1 favorite]

What is the funnel made of? Can you line the funnel (or fashion a new funnel) with something like parchment paper or weigh paper that resists sticking? That's if the powder isn't clumping, of course, and the most friction is coming from the funnel, as you say.

Putting the bottle and funnel on something like a vibration plate may help shake powder through a small opening, but I'm not sure how much shaking helps you.

Would shortening the nose of the funnel help?
posted by supercres at 11:41 AM on November 24, 2020

piping bag +1
posted by j_curiouser at 11:47 AM on November 24, 2020 [1 favorite]

Maybe baby feeding syringes?
posted by showbiz_liz at 11:47 AM on November 24, 2020

If you have a clothes dryer, the vibration from it can help the powder fall into the bottle. Sure, you'd have to set up your filling station in the laundry room....but I bet there are other sources of vibration that you could find a way to use.

Second, gotta let the air out of the bottle so prop a straw or toothpick to make space for that.

My other piece of advice is to figure out the weight of powder that goes into each bottle, and measure the exact amount of powder for each filling, so you aren't having to check "is it almost full yet?" because that checking is demoralizing and time consuming. When the funnel is empty, the bottle is done.

I would line up a dozen or 50 bottles on the top of the dryer, set up a parchment filter with a toothpick taped to it in each bottle neck, weigh the powder into each funnel, and turn on the dryer.

Check first with one bottle to make sure the bottles stay upright when dryer is shaking. And also to see how long it takes the shaking bottle to fill.

For science.
posted by bilabial at 11:49 AM on November 24, 2020 [7 favorites]

If you think moisture in the air is part of the problem, can you run a dehumidifier in the room where you're working?
posted by Winnie the Proust at 11:56 AM on November 24, 2020 [2 favorites]

The powder in question gets very sticky as soon as it's in contact with air (I'm guessing the moisture in the air).

Are you in a tropical climate? At this time of year I'm guessing it's more of a static cling issue. Adding humidity might actually help your situation. There are electrostatic generators that can assist with neutralizing the charge around you but they're very expensive for what you're trying to do.

What kind of funnel are you using? Something nylon or plastic? Try a metal one with a metal stick to stir/assist.
posted by mookoz at 12:14 PM on November 24, 2020 [1 favorite]

I'm guessing you could find a Amazon.com : wood auger bit that would fit inside a tube of some sort that would both fit in the neck of the bottle with a little room on the side for airflow. Build some sort of funnel/crank on the top. You could probably get it down to X cranks and a bit more. Good idea. But probably has to be engineered a bit to avoid cutting into the tube or keeping centered.

For a funnel in general I'd try teflon coated foil over maybe cardboard. It's pretty slick. Other materials should be checked.

Like the previous thick liquid vs funnel... velocity could help stop sticking. If you can get it into the bottle while it's still going fast enough to not get stuck to something else on the way down... Eh? it'll probably help.
posted by zengargoyle at 12:44 PM on November 24, 2020 [1 favorite]

If it's a static buildup issue, a metal funnel might help. If it's a moisture issue, a PTFE funnel might help.
posted by Dmenet at 1:11 PM on November 24, 2020 [2 favorites]

Can you put a dehumidifier in a closet or small room and work in that area? Or run an AC unit, which will also make the air very dry?

Caveat: I live in an area with very low humidity, and an AC can easily get the humidity in a room into the single digits. I don't know if it would work like that somewhere more humid.
posted by yohko at 1:53 PM on November 24, 2020

Wikipedia says it's hygroscopic.

You might try building a little dry working area. A clear plastic rubbermaid style tub with some holes cut in it just larger than your arms, plus a hole cut for the power cord of a tiny dehumidifier might work pretty well. You'd need to cover the holes when not in use, and you don't want to leave the dehumidifier running unattended as they get a bit warm.
posted by gregr at 2:30 PM on November 24, 2020 [1 favorite]

If this is a hygroscopic powder, ideally you're going to need a moistureless atmosphere to pack in. There are expensive machines that will absolutely provide this for you (if you're doing thousands, might be worth checking out). There's also a DIY solution that I've seen recommended that costs under $250. You can get a glove bag from Sigma Aldrich or another scientific supply house, and some inert gas (likely nitrogen or CO2) from your local AirGas or similar supplier. Put your (closed, sealed) packages of powder, along with your funnel, bottles, implements, etc. into the glove bag and squeeze all the air out, then refill the bag with the inert gas. You can then reach into the bag with the gloves built into it and portion out your powder without it getting sticky. Once in this moistureless environment, perhaps a pastry bag or a similar solution would work too.
posted by ourobouros at 3:49 PM on November 24, 2020

When filling capsules, in a pharmaceutical setting, that's what incipients are for - incipients being other ingredients that make your active ingredient flow better, be more stable, etc.

It can be quite a complicated science formulating which incipients to use when actually making capsule pills.

How pure do you need your material to be?

Another thing to consider is - how easily does the material come out of the bottle for the end user?

Common incipients to improve flow include silicon dioxide (SiO2), magnesium stearate, talc (Mg3Si4O10(OH)2), or various combinations.
posted by porpoise at 4:12 PM on November 24, 2020 [1 favorite]

how easily does the material come out of the bottle for the end user?

That was my immediate thought as well. If it's a sticky powder on the way in, it might well become an immovable clogged lump before it has a chance to come out.

Would it perhaps be worth your while to look into alternative containers? Small vials with no neck, for example?
posted by flabdablet at 4:29 PM on November 24, 2020 [4 favorites]

Response by poster: Thanks everyone, lots of good suggestions to try out!

I don't think mixing other ingredients in is viable right now as i would need to test the effects long term. The powder is used to make art prints (cyanotypes) so the recipe needs to be pretty stable.

The powder doesn't have to come out again, the user adds water directly to the bottle to get a useable solution, so that part at least is not an issue.

I've got a weighing machine that already shoots out the correct amount of powder for me, that goes pretty fast, but then it takes a while to push it down the funnel.

I've just ordered metal funnels and teflon coated foil to give it a first try, let's see if those cheap measures make a difference, if not I'll step it up to dehumidifiers.
posted by PardonMyFrench at 11:11 PM on November 24, 2020

Try making a paper funnel! I had this issue yesterday when my powder was sticking to plastic due to static and I had to make a paper funnel.
posted by DarlingBri at 12:10 AM on November 25, 2020

A friend worked on a plant which bagged powdered sulfur for retail sale. The basic setup was a funnel-shaped hopper with a vibrator mounted on one side. I suspect that if you have a massager or ... well, a vibrator, you could use it for this. An old electric razor would probably also vibrate things enough, and an electric toothbrush might work, though I'm not sure how much they vibrate.
I'd put as little powder as you can in the funnel - possibly you could find an appropriate sized measuring spoon or just make a mark on your funnel. Powders make bridges (in a phenomenon known as 'bridging') which can span surprising distances - sulfur can bridge about 27 feet. I don't imagine your powder will be as bad.
Oh - Bilabial mentioned this. I'll leave it here to point out that you don't need to rely on your dryer.
posted by AugustusCrunch at 1:34 AM on November 25, 2020 [2 favorites]

Tape your funnel to something that vibrates, like a beard trimmer.

If the powder is safe to heat, keep it warmer than the ambient temperature.
posted by kleinsteradikaleminderheit at 3:53 AM on November 25, 2020

(Note if you try to do further research: inactive ingredients in pharmaceuticals are actually called *excipients* )
posted by Green Eyed Monster at 2:03 PM on November 25, 2020 [1 favorite]

*excipients* - thanks, brainfart on my behalf

Alternately, if the container doesn't have to be completely filled - is it possible to press the material into a pellet/ stick and just drop that into the bottle?

Especially if it likes sticking to itself, you might be able to use a silicone mold for candies, or borrow a pill press. There are also smaller (and cheaper) handheld pill press units, too.
posted by porpoise at 2:58 PM on November 25, 2020 [1 favorite]

If you could give us an idea of the specific quantities of powder and some actual measurements of the bottles and their necks, that would help come up with suggestions for which handy household items to press into service.
posted by flabdablet at 10:07 PM on November 25, 2020 [2 favorites]

Response by poster: Thanks everyone for the helpful suggestions!
So the metal funnel and stick are already helping a bit.

The glass bottle are 100ml capacity and need to be filled about a third of the way with the sticky powder, through the narrow neck (DIN 18, the opening itself is about 8mm diameter). I hacked the funnels so i can glue them to the actual caps that screw on the bottles, with a hole drilled in, so the funnels can be attached very securely.

I've ordered one of those vibrating plates for exercise that will be here in a couple days, I'm hoping to use it as a crate on it with spots for holding the bottles while the powder shakes down.
posted by PardonMyFrench at 3:12 AM on November 27, 2020

I bet one of these 6mm tube brushes with the loop clipped off and the shaft chucked up in a cordless drill would shove stuff down the neck of your little funnel way way faster than a stick. Might want to put the drill in reverse, depending which way the spiral is wound on the brush.
posted by flabdablet at 7:39 AM on November 27, 2020

I just did this with baking soda and a standard little plastic funnel.

Vibration worked as usual. Bashing the funnel with a knife to knock things loose.

Stirring with a bamboo skewer worked much better. A bit off-axis so that a bit is rotating down in the narrow bit, there's a pivot, and the above bit is stirring up the powder. That got things going rather quickly.

YMMV
posted by zengargoyle at 5:38 PM on November 30, 2020