VDB classic mixing

[andrewfrith]

I just mixed some VDB traditional last night using

Part A
33ml distilled water
9g Ferric Ammonium Citrate

Part B
33ml distilled water
1.5g of Tartaric Acid

Part C
33ml distilled water
3.8g silver nitrate

I got a milky white precipitate down the bottom of my bottle..is this unusual, should i filter this off before use?

-andrew

 

[Aggie]

..

 

[Ole]

Aggie's right, except for the last paragraph

Don't filter it off, you'll lose some of the silver. Just let it sit for a while, stirring occasionally. If you're as lazy as I am, a magnetic stirrer for about half an hour should get it all dissolved.

 

[andrewfrith]

Thanks Aggie, thanks Ole..i did what i thought was adequate stirring whilst adding C but i guess maybe not enuff...i did make a VDB liam lawless contrast control mix (mention in PF #8 i think) mix too with ferric citrate in the A and that bottle looks completely dissolved, even the ferric citrate seems to have dissolved overnight on that one..i guess i'll keep stirring on the classic and hope that it dissolves.

BTW: does it matter what kind of lighting conditions you do the mixing under? does it need to be subdued lighting or is the mixture not sensitive at this point?

regards
-andrew

 

[Ole]

Lighting conditions matter. While not as sensitive as the dried "emulsion", the mix is sensitive to light. The raw chemicals (ammonium ferricitrate and silver nitrate) are sensitive as well, and should be stored dark.

I wouldn't worry about incandescent lights while mixing, but fluorescent or daylight would be a bad idea. Subdued light shouldn't be necessary, except if the mixing takes a very long time.

(Yet another reason why I love my stirrer - I start mixing, then leave the room and check it every once in a while if it takes a long time to dissolve)

 

[andrewfrith]

one of those lab mixers looks very handy Ole...its been 3 or 4 days since i mixed the VDB classic and it still has the milky preciptate down the bottom...ive been intermittedly giving the bottle a shake over the last couple of days but it looks like it doesnt want to go into solution...what is that precipiate, silver citrate or something? do u think my mix is still good to go? should i just pipette off some of the clear solution from the top before coating?

regards
-andrew

 

[Ole]

Most silver precipitates are milky - like the milky stuff you see when you wask the print. That's the surplus silver reacting with trace impurities in the tap water! The first times I tried this, I couldn't see any cloudiness at all. Then the waterworls put another source on line, upped the chlorine slightly, and hey presto! Cloudiness...

The best way to see if it works is to try it. I mixed my first (and so far, only) mix with "brown" ammonium ferricitrate, but it still works. I've "tweaked" it a little since then (added more water, mostly, and a few drops of AGNO3 solution and a smigeon of hydrogen peroxide), but I'm certainly not going to throw it away.

There's lots of silver in the solution, and it takes incredibly little to form visible precipitate. Try it, then start worrying if it doesn't work.