collodion problems

[scratched&grainy]

Hi,
I wonder if anyone out there can help me?
I tried doing some wet plate negs today. The first few went great. I metered with an analogue camera and got a quarter of a second at iso 20 at f/8. not knowing the iso of the collodion i figured id stop down to iso 1 and a quarter which would give an exposure of 4 seconds. This was fine. But using the same maths for flash or for an exposure of 30 seconds i got nothing. so i couldnt work out if i was exposing wrong or if id done something wrong with the chemistry? I dont recall contaminating anything. I repeated the same shot as the one that turned out well and got an image that was barely visible. So, im thinking, maybe i need to add more silver nitrate to the bath? all in all i only took about 10 shots. My collodion formula is 100ml alcohol, 120ml collodion and 100ml ether. My silver nitrate bath is 1l distilled water, 90g silver nitrate, 10 drops of nitric acid and 15 drops ammonium hydroxide, my developer is 400ml 10% vinegar, ferrous sulphate 10g, 20g alcohol and 20g distilled water.any help greatly appreciated,
thanks,
Mark

 

[ScottPhoto.co]

Keep in mind that collodion only reacts to UV light. A lot of strobes have a UV protective coating and don't allow UV spectrum light to pass. This will definitely affect your exposure. Collodion work using strobes takes a LOT of light and many people fine success with continuous light using UV spectrum bulbs.




Tim
www.ScottPhoto.co

 

[scratched&grainy]

Hmmmm. i wil change the light source. But how come shot 1 is fine and shot 3 is nothing?

 

[illumiquest]

I'm a little confused as to what you're asking but have you measured the SG of your silver bath? When silver drops below it's working strength, in my experience it does so rapidly, within a few plates.

 

[scratched&grainy]

ok, great, i added silver nitrate and the bath works again. but i have another problem. my first image was the flower in the glass bottle. not great but something i can work with.the second image was the pylon - barely visible. so i added the silver nitrate and got the following 2 images. the roughness is due to the fact that after adding the silver nitrate the film wouldn't stick to the glass so i started experimenting with egg white and that is something that i can work on. the problem is the really thin negative-almost nothing there. so my question is: to get a punchier, more contrasty negative do i change the proportion of the salts in the collodion, change the developer or something else? Im pretty sure that i'm exposing right. my collodion is ether100ml, alcohol100ml and collodion120ml plus cadmium bromide 1g, ammonium bromide 1g, cadmium iodide 1g, ammonium iodide 1g. my developer is a negative developer.
thanks
nb. the images were scanned as negatives.

 

[craigt]

To be honest, I don't know why you're adding the nitric acid. The only time it should be added is if your distilled water is extremely alkali (e.g. from a limestone aquifer) and as a very last resort. Your silver bath can actually perform just fine for negatives when at Ph5-6 but generally should be Ph3-4.5 for positives. Then you're adding ammonium hydroxide which will neutralised your bath?! Essentially you're acifiying it with nitric acid (which will dramatically slow down your exposure times) and then neutralising it with ammoinium hydroxide....it doesn't make any sense.

I think if you simply made your 9% silver bath with 9g silver nitrate and 100ml distilled H2O (90g silver nitrate/1000ml Distilled H2O) you'd be getting great plates.

 

[scratched&grainy]

I added the nitric acid by mistake. I read a recipe that said i should measure the ph of the silver nitrate and then add nitric acid to bring it up to the required ph for negs. So i measured the ph and added the nitric acid (although i thought this was weird) and the ph went down to 2. So then i had to rescue the bath by adding ammonium. So that's the story of my buggered up silver nitrate. Now im thinking of maybe adding more salts to bring up the contrast. Bad idea?or should i just bin it and start again?

 

[craigt]

Bad idea...yes! Leave your collodion and developer formula's alone and get your silver bath working the way it should.

You can save your bath, never bin it. First things first...do a litmus test and check the Ph. If it's anywhere around Ph4.5 you'll be fine. You might as well sun your bath and remove any organic material that precipitates out. Filter it until your filters are dead clean and then put it to work.