Gelatin Questions

NedL · Dec 27, 2015

1) What is a good way to measure dry gelatin into container for mixing? The granules have a lot of static cling and they stick to a spoon or paper when transferring. Also they stick to the side of the container I'm putting them into, which leads to the next question.

2) If I agitate the container before or during the blooming, it introduces bubbles. If I don't agitate or shake or swirl the container, I end up with a few undissolved granules ( the ones that stuck to the side of the container, I think! ).

3) Any good tips for avoiding little bubbles in the gelatin?

4) This could be my imagination, but today I coated two sheets of paper: the first sheet of paper had been acidified in weak acetic acid, and the second paper was coated with gelatin that had a little citric acid mixed in. My impression was that the gelatin set up faster than usual, and it caused problems not having enough time to smooth it all out or push all the bubbles to the side. Does pH affect how quickly gelatin sets?

I haven't had much trouble with bubbles before today, but today I was trying to agitate the gelatin to avoid dry granules, so I introduced a different problem!

Photo Engineer · Dec 27, 2015

Dry grains (slugs - because they look like garden slugs) will dissolve given time and heat. You should not shake. Stir. Use a magnetic stirrer if possible. Heat no higher than 40C with good mixing. Do not allow it to stick to the bottom of the container. Heat, chill, pH and length of melting all affect viscosity and setting time. The Bloom Index is critical to set time, melt time and viscosity. In making emulsions, we usually use a BI of 250.

Filter through a gold coffee mesh to get rid of solids and bubbles. Also adding a drop or two of t-Butyl Alcohol will remove bubbles.

PE

cliveh · Dec 27, 2015

Photo Engineer said:
Dry grains (slugs - because they look like garden slugs)PE

They don't look a bit like garden slugs, they look more like a chopped up worm.

NedL · Dec 27, 2015

Thank you PE. I'm using BI 250 photo-grade gelatin. Today I shook the container during blooming which was obviously a big mistake! I was mixing up 10ml at a time in plastic film canisters.

It sounds like I should keep it at melting temperature a little longer and stir carefully. The gold coffee filter is a good idea: thanks! I don't have any t-Butyl Alcohol, or any alcohol for that matter, and I'm not sure where to get it.

I'll try with more slugs tomorrow

Photo Engineer · Dec 27, 2015

If you are not using any silver or mercury salts, then Vodka will do for a defoamant!

PE

Photo Engineer · Dec 27, 2015

cliveh said:
They don't look a bit like garden slugs, they look more like a chopped up worm.

They look exactly like our local slugs and not the red brown worms!

If you had done it as often as I have, you would not question that!

I'll bet you don't know what a syrup is either!

PE

cliveh · Dec 27, 2015

Photo Engineer said:
They look exactly like our local slugs and not the red brown worms!

If you had done it as often as I have, you would not question that!

I'll bet you don't know what a syrup is either!

PE

Well my understanding of a syrup is a thick, viscous liquid consisting primarily of a solution of sugar in water. What is yours?

NedL · Dec 27, 2015

Photo Engineer said:
If you are not using any silver or mercury salts, then Vodka will do for a defoamant!

PE

No silver or mercury salts, but an iron salt: ferric ammonium citrate. A couple drops of vodka still okay to try?

Photo Engineer · Dec 27, 2015

Yes, Vodka is OK in this case.

In photography, a thick concentrate used for any purpose is a syrup. Thus, HC110 concentrate is a syrup. See the other thread.

OTOH, cooled gelatin is called a "gel".

PE

gone · Dec 27, 2015

Syrup is what I used to judiciously pour on top of my pancakes, back when I ate pancakes. On this !#*^!!&* healthy vegetarian diet, most everything I eat looks and tastes like slugs (I guess). But I'll try the vodka, and it won't be a couple of drops either. Thanks for the nite cap tip :]

Andrew O'Neill · Dec 27, 2015

Isopropyl alcohol should work too, no? I use it to take care of micro bubbles when making glop for carbon transfer printing.

NedL · Dec 27, 2015

I've got some isopropyl alcohol here, I think it's the more common 70% variety. Thanks all!

Photo Engineer · Dec 27, 2015

Yep, IPA should work, as long as it is not denatured with any ingredient that causes cloudiness when mixed with water.

That can do "things" to photographic processes, but IDK which ones.

PE

pdeeh · Dec 28, 2015

I note that one supplier of photographic gelatin offers both 225 and 250 bloom.

Under what circumstances might one be preferable to another?

ced · Jan 4, 2016

I notice you chaps and the alcohol are zig zagging a bit, well here is a fun one and hope it doesn't stray too far from the thread
Apologies to those that are familiar with this joke.
http://joek.com/jokes/joke_8.shtml

Photo Engineer · Jan 4, 2016

pdeeh said:
I note that one supplier of photographic gelatin offers both 225 and 250 bloom.

Under what circumstances might one be preferable to another?

These are close to identical. Viscosity and spread factor (laydown at a given gel %) are important. The 225 will be less viscous than the 250, and that is about it.

PE

pdeeh · Jan 4, 2016

thanks PE

Tom Taylor · Jan 5, 2016

There's an anti-static wipe of some kind that labs use on measuring cups to prevent particles from clinging to the cup. I read about it in the manual that came with my Ohaus digital scale. I've been meaning to but so far haven't looked for a supplier. If you find one, please post a link.

Thomas

NedL · Jan 5, 2016

Thanks Tom, I'll try to look into that.

I'm doing a little better with undissolved slugs and bubbles just by being careful, looking at everything closely, and stirring carefully.

NedL · Jan 5, 2016

I've found several laboratory manuals for micro-balances and other delicate measurements that mention using "kimwipes" to clean instruments, forceps, and prevent static. The kimwipes have something called "lintguard" that is an "antistatic polyshield", whatever that means. I remember seeing kimwipes around the lab when I was in college... The boxes are inexpensive and sound like they would be useful for many delicate cleaning tasks and prevent static at the same time. I'll probably order some.

Photo Engineer · Jan 5, 2016

I use just plain rolls of paper wipes. They do the same at GEH.

PE

NedL · Jan 5, 2016

Hi PE, I was hoping the wipes might eliminate static so that the dry gelatin and ferric ammonium citrate I'm using don't stick to the side of the container. OTOH, I followed your advice about stirring carefully, and I let the warm gelatin solution gently "wash" the sides of the container, and I don't seem to be having problems anymore, so maybe this is much ado about nothing

It still would be nice to measure the gelatin and FAC without it sticking to every spoon/paper/scoop I try to transfer it with.

Actually, I have to chuckle imagining what you must think as a chemist with decades of lab experience, then here's me on the internet and I can't mange to get the gelatin from it's bottle to the container on my scale without some of it sticking to and dropping off the spoon...

Seriously, thank you for being so helpful here at APUG. It is greatly appreciated.

Vaughn · Jan 6, 2016

I do not quite understand the problem -- once one adds water to the powder, there will be no more static clinging. Everything gets wet, everything dissolves. And the amount that clings is not significant to the total amount. Guess I should just be thankful I live in a humid climate....

Try weighing and handeling chemicals with paper. I use cupcake papers for weighing out chemicals -- never noticed any static cling with those. I weigh out the gelatin in the cupcake papers, I pour it into water...seems fairly straight forward.

NedL · Jan 6, 2016

Hi Vaughn, I've never noticed it before the last couple weeks either; I think our house has much drier air than usual because the furnace has been running a lot lately, leading to more static. It's even a little hard to weigh the gelatin precisely, because it sticks to whatever I use to transfer it out of its container ( as does the AFC I'm using ). I'm using plastic film canisters to mix up the gelatin, because the mixture is somewhat light sensitive.

The trouble started when some dry gelatin stuck to the side of the canister, so it was not in the water during swelling.. and led to little granules or slugs of undissolved gelatin when I coated my paper. I think the problem is solved now, but at first I made a new problem by shaking the canister and introducing bubbles.

I should take a photo of it so you can see how extreme it is. If I stick a plastic spoon or a strip of folded paper into the gelatin to transfer it, it comes out completely covered in gelatin on all sides, top and bottom, even sticking to the thin edges! Then it starts falling off from underneath as I'm trying to weigh it. It sticks tenaciously to the inside wall of the film canister too.

Until recently, I just used a folded strip of paper as a scoop and the gelatin pours neatly and easily out of it, no problems. And I don't remember it ever sticking to the sides of anything, I usually use clear plastic disposable cups to swell and mix gelatin.

Edit: I tried to take a photo but I can't hold the camera and the scoop at the same time easily... would have to set up a tripod. But playing around with it, it is wild! Inside the jar of dry gelatin, the little "slugs" all line up around where the paper or spoon touches them, almost like iron filings and a magnet. And where they stick to the paper, they are standing on end, sticking straight out. Underneath there are "chains" of gelatin slugs end-to-end nearly a centimeter long. Then I touched the paper to the fur of my dog ( thinking to make the effect even stronger ) and when I put the paper in the jar, the gelatin jumped away from it. Apparently my dog is the opposite polarity! Crazy!

Vaughn · Jan 6, 2016

It is obvious that I am spoiled by our constant 60% relative humidity! (plus or minus 10%)

I mix gelatin for carbon printing...not quite as fussy as silver emulsion making! I do not worry about bubbles at this stage -- I use a stirring paddle and blend the heck out it! I am making a 12% gelatin mix, food grade. I wait 30 minutes for the water to completely absorb, then put it in a 110F water bath until it melts. All of the mixing from this point on, is with a magnetic mixer -- after adding the sugar and pigment (and some isopropyl alcohol), I have it sit in a water bath for several hours before pouring the tissues. The glop is filtered thru several layers of stocking material right before pouring the tissues to filter out such things as beard hairs and bubbles.

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