Dry chemicals like rocks.

PHOTOTONE · Feb 4, 2007

Some of the support powder chemicals (not the developing agents) for mixing home-brew developers come from the vendors not as nice dry powders, but often a mixture of powder and "chunks" that can be as hard as stones. i was wondering if any of you use a mortar and pestle to re-pulverize the chunks? Or what do you do? Ice pick in the jar?

dancqu · Feb 4, 2007

PHOTOTONE said:
Some of the support powder chemicals ...
come from the vendors not as nice dry powders,
but often a mixture of powder and "chunks" ...

I've never had that problem with chemistry supplied
by Photographer's Formulary. Mortar and Pestle. Dan

Mick Fagan · Feb 4, 2007

I've had some problems over the years, some chemicals that come to mind are:-

Potassium metabisulphite, had to use an ice pick, but it went into solution quite readily.

Sodium tetraborate, I had a very low grade, it was almost impossible to get it to go into solution, I resorted to a mortar and pestle. I purchased some analytical grade which is almost as fine as a powder, it virtually dissolves in minutes with little stirring.

Ammonium thiosulphate, another ice pick job, always leaves a residue, which I filter out with a cheap coffee filter.

Mortar and pestle is quite handy sometimes, bought my latest one from Aldi,

Mick.

Photo Engineer · Feb 4, 2007

Just be careful. A mortar and pestle work fine, but the mortar is porous ceramic and can pick up particles of chemical. When washed the chemistry seeps into the pores and can accumulate there.

So, make sure it is clean and dry when you use it and make sure you clean it well after use.

PE

Jim Fitzgerald · Feb 4, 2007

Photo Engineer said:
Just be careful. A mortar and pestle work fine, but the mortar is porous ceramic and can pick up particles of chemical. When washed the chemistry seeps into the pores and can accumulate there.

So, make sure it is clean and dry when you use it and make sure you clean it well after use.

PE

PE, is there something more suitable? I am having the same problem with some of my dry chemicals. Thanks.

Jim

Joe S · Feb 4, 2007

I had the same problem with some chems that I ordered as well, luckily I was able to leave it in the plastic bag and gently crush it until it went into bee bee sized pellets, I use a magnetic stirrer to mix my chems so once I had it down to that size the stirrer took care of the rest, and it makes mixing chems a lot easier and faster.

Photo Engineer · Feb 4, 2007

Joe has the answer. Crushing in a baggie or several baggies does the job well and avoids any possible cross contamination from a mortar. I have one, but I rarely use it. I prefer to use a very sharp tool to break up lumps, but I seldom have lumps.

PE

PHOTOTONE · Feb 4, 2007

Hadn't thought of putting the lumps in a few plastic bags and crushing. Good idea....and can be implemented with the materials at hand!

PHOTOTONE · Feb 4, 2007

dancqu said:
I've never had that problem with chemistry supplied
by Photographer's Formulary. Mortar and Pestle. Dan

Well, that is the vendor I use, and a couple of the chemicals came in sealed jars but still had big lumps.

PhotoJim · Feb 4, 2007

Some chemicals are hygroscopic, i.e. they absorb water. These chemicals tend to become hard chunks of material (some harder than others).

Potassium bromide seems to be this way too. I always have to break the chunks using a clean screwdriver or some such tool.

The chemicals that tend to do this will do so over time, even if they come free-running. Keep them as sealed as possible to procrastinate this moment as much as you can.

Ronald Moravec · Feb 4, 2007

Generally if yu keep air away from it, it will not cake. Put the chem in a plastic bag, tighten the excess plastic, and put back into original bottle.

Heavy plastic bag and rolling pin will cure it.

pnance · Feb 4, 2007

Mountain Home Biological sells a glass mortar and pestle, fairly reasonable tool.

Mick Fagan · Feb 4, 2007

Does anyone know how chemists clean their mortar and pestle equipment between different medicines, or has that gone by the politically correct wayside as well?

Mick.

dancqu · Feb 4, 2007

pnance said:
Mountain Home Biological sells a glass
mortar and pestle, fairly reasonable tool.

I've both ceramic and glass. Personally
I think PE worries too much. A good rinse
in warm water should do for ceramic. Buy
two or three and dedicate. Keep track
of which grinds what.

Potassium compounds as a general rule are
more hygroscopic than the sodium. I had some
Potassium Bromide cake up. Weighed it with
bottle to 0.01 gram accuracy then baked
it and bottle. After baking, no difference.
Likely less tha 5 grams were involved.
Evidence to me though that the
most minute amounts of H2O
may cause caking. Dan

Photo Engineer · Feb 4, 2007

dancqu said:
I've both ceramic and glass. Personally
I think PE worries too much. A good rinse
in warm water should do for ceramic. Dan

Dan, grind up some sodium iodide or sodium bromide in a mortar and pestle, then wash well and set to dry.

Then, soak in some distilled water and pour a solution of silver nitrate into the wash water to see what happens.

Sometimes, things are ok, and sometimes you get a precipitate or cloudiness indicating that the pores of the ceramic have some of the halide trapped. It depends on the quality of the ceramic. The glass ones are the best!

I would have 2, one for developer chemistry and another for fixer chemistry. I would also prefer to wash one that was used with organics with an organic solvent a few times along with a water wash. Hydroquinone is really hard to get out of a mortar are a few other chemicals that have low melting points or are hard to dissolve in water. Benzotriazole comes to mind as being in this category, but I could name a few others.

I'm being quite serious about this for anyone who wants to use one of these. I highly recommend using one, but one that is glass, and that will eliminate the problem.

And, I'm not saying what will happen, I'm saying what might happen. I have one but don't use it currently for this very reason.

PE

Mick Fagan · Feb 5, 2007

Great information PE, many thanks.

I'll look for a couple of glass units.

Mick.

donbga · Feb 5, 2007

Jim Fitzgerald said:
PE, is there something more suitable? I am having the same problem with some of my dry chemicals. Thanks.

Jim

Use a glass mortar and pestle. They aren't porous.

PHOTOTONE · Feb 5, 2007

I can't think of any developing agents I have that are clumped. It is only the various bromide, sulfite, carbonate items that sometimes clump.

Photo Engineer · Feb 5, 2007

Here is the word from our local pharmacist. I should have remembered this myself.

For chemical purity, you use what is called a WEDGEWOOD mortar and pestle. This type is roughly glazed inside the mortar and the pestle is roughly glazed to the tip.

He said that he has had to resort to cleaning a mortar and pestle with acetone to remove some drugs but that is even though he uses a Wedgwood mortar and pestle. He does not use a regular "Food Grade" mortar and pestle that is unglazed on the inside of the mortar and has an unglazed pestle or pestle tip. He reminded me of this and said that we should not use the "Food Grade" type at all for chemicals.

It has been so long since I've used one, I had forgotten. We used ball mills at EK to 'soften up' chemicals. They use a ceramic or steel jar with either ceramic or steel balls to mechanically roll the crystals and lumps into a fine uniform powder.

PE

dancqu · Feb 5, 2007

donbga said:
Use a glass mortar and pestle. They aren't porous.

Agate is another good choice. More expensive. Dan

Dry chemicals like rocks.

Privacy & Transparency

Privacy & Transparency