View Full Version : Pyro solution sediment

Colin Robertson
17-Jun-2007, 15:31
Having decided that FP4 in Ilfosol lacked 'mojo' I decided to try Pyro (well, seems like everyone else is . . .) My developer of choice is sold by a company called retrophotographic in the UK, branded as 'Original Retro Pyro'. It's Pyrogallol and Metol based, supplied as two powders to be mixed as solutions A and B. In use they are diluted 1+1+50. FP4 shows good contrast, with a distinct brown stain and crisp grain.
Anyhow- today I shot some stuff and only whilst mixing the working solution did I realise that the solution B was full of crystals. A mild shaking did nothing to re-disolve them. With nothing to lose I went ahead. The resulting negatives show good density and appear to have a full tonal range (actualy, they look kinda nice) although I have not yet attempted to print them.
So finaly the question- since there is very clearly crystaline sediment in solution B, 'something' is no longer in solution, but it works. What is my sediment likely to be? If its precipitation out doesn't stop the developer working, why is it there?
More generally, do Pyro solutions need some particular care in storage?

steve simmons
17-Jun-2007, 16:10
With PMK, and I do not know what you actually have, a little sediment in the B solution does not make any difference.

steve simmons

Paul Metcalf
17-Jun-2007, 17:11
I bet that's Sodium Metaborate that's settled out of solution. Warm the solution up and then shake/stir, it will dissolve again. I agree with Steve, it doesn't make a difference. As far as storage, the pyro is in the first part (A) and will reach a certain level of oxidation (it will look yellow) and stop. It's still very active. I use brown bottles (left over from a high school chemistry lab that was cleaning house) with lid.

Colin Robertson
18-Jun-2007, 00:13
Thanks guys. Swift and informative.

Joseph O'Neil
19-Jun-2007, 05:26
If in doubt - with any photo chemistry - buy some cheap paper coffee filters and filter your chemistry before mixing.

19-Jun-2007, 05:37
The material -- crystals -- in PMK part B result from the super saturated solution. It is very sensitive to temperatue change and you only have to turn your back and the crystals start to form.

I recently took the remainder of my part B, heated it and dissolved the crystals and added an equal quantity of distilled water to it. It has not altered the results of the PMK as instead of 1.2:2:80 , I now use 1.2:4:80.

I am still getting a slight precipitate but nothing like before.

I have taken to letting the part B sit in very hot water to dissolve those crystals back into solution while I prepare other things.

steve simmons
19-Jun-2007, 06:33
PMK is an A and B solution. I use it 1:2:100.

steve simmons

19-Jun-2007, 07:40
PMK is an A and B solution. I use it 1:2:100.

steve simmons

So do I Steve unless I need to get particular results

A- 1.2mll
B - 4 ml [Twice the water as the formula states when chemistry is mixed] Diluted as explained above.
Water - 80 ml.

This is the mix I use for Foma 200

In BTZS tubes

Colin Robertson
19-Jun-2007, 11:04
Okay- the notion of precipitation from a supersaturated solution makes perfect sense.
On the basis that everything in the stock solution is there for a reason, it is best to keep all the elements in the solution, and so active. For now, I will make do with warming and shaking solution B prior to use, to redissolve the crystal precipitate as far as possible.
When I mix my next batch of developer I reckon I might make B twice as dilute, to reduce the likelihood of precipitation. Assuming this makes no significant difference to keeping properties, I then only need to change my working proportions to 1+2+50.
Once again, thanks for the suggestions.