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sanking
11-02-2006, 09:18 PM
Ron,

I have been experimenting recently with a a silver-iron based emulsion that has very little color, hand coating with a brush.

Can you recommend a coloring dye that would not interfere with the process and allow me to better see the coating before it dries.

Sandy King

Photo Engineer
11-02-2006, 09:39 PM
Sandy, I use food color from the supermarket. I have to use more surfactant because the colorant has some antagonistic properties to proper spread.

I would also suggest erythrosine as a very strong magenta colorant and very water soluable. I've used it, but it is about $25 / gram. But OTOH, you only need about 100 mg to make 100 ml of solution.

PE

sanking
11-02-2006, 10:23 PM
Sandy, I use food color from the supermarket. I have to use more surfactant because the colorant has some antagonistic properties to proper spread.

I would also suggest erythrosine as a very strong magenta colorant and very water soluable. I've used it, but it is about $25 / gram. But OTOH, you only need about 100 mg to make 100 ml of solution.

PE

Hi Ron,

Thanks for the information. I will try the food colors tomorrow. Any brand better than another?

Sandy

photomc
11-03-2006, 06:49 AM
Hi Sandy,
Don't know if it matters in your case or not, but you can find a paste food coloring as well as the liquid sort - but you may already know that. Just thought it might help (info from the wife, she says it mixes better when cooking and does not make it watery)

rongui
11-03-2006, 07:47 AM
Sandy, I use food color from the supermarket. I have to use more surfactant because the colorant has some antagonistic properties to proper spread.

I would also suggest erythrosine as a very strong magenta colorant and very water soluable. I've used it, but it is about $25 / gram. But OTOH, you only need about 100 mg to make 100 ml of solution.

PE

"McCormick Assorted Neon Food Colors" has 4 dyes in the kit. One of the bottles is FD&C Red #3 and from my research on the net is erythrosine.

Hope this helps,
Ron

Photo Engineer
11-03-2006, 08:56 AM
Guys;

I have tried the liquid and the paste forms of the food dyes. The paste form takes quite a bit more tinkering than the liquid form due to the additives there to form the paste. I used the word paste, but 'gel' is probably more applicable here.

They both work though.

Erythrosine is a food dye. That is why I use it. It is the least toxic and expensive of all of the dyes for use in experiments of any sort requiring a good dye.

PE

photomc
11-03-2006, 12:30 PM
Thanks Ron..

sanking
11-03-2006, 12:31 PM
"McCormick Assorted Neon Food Colors" has 4 dyes in the kit. One of the bottles is FD&C Red #3 and from my research on the net is erythrosine.

Hope this helps,
Ron

Well, this is what I found, and I just coated a piece of paper using it. I had just one drop to 3ml of coating solution and it made the almost transparent sensitizing solution much easer to see and coat.

Now I am wondering if the red/orage color is going to cause an increase in contrast by blocking UV light? Will have the answer soon as I am about to expose the paper.

Sandy

sanking
11-03-2006, 01:02 PM
OK, I finished the test. It looks like the color did not change speed and contrast very much, if at all. But the paper is stained with the red color and it looks like it may not all wash out.

Sandy

Photo Engineer
11-03-2006, 01:06 PM
Yes Sandy, some of the food dyes will mordant to the paper support. Sorry. The only other way to do this is use a pigment. You might consider the pigment used for colored carbon. Just use a tiny amount to make the coating visible though.

OTOH, can you coat on YUPO? I doubt if the dyes would mordant to that support.

PE

sanking
11-03-2006, 01:31 PM
Yes Sandy, some of the food dyes will mordant to the paper support. Sorry. The only other way to do this is use a pigment. You might consider the pigment used for colored carbon. Just use a tiny amount to make the coating visible though.

OTOH, can you coat on YUPO? I doubt if the dyes would mordant to that support.

PE

I could probably coat on Yupo, but for printing I prefer all rag papers.

Guess this is one of those times when the solution is worse than the problem! Though I will give the pigment idea a try. Got plenty of that on hand.

Sandy