Re: Diazo Photo Emulsion Chemistry & Gum Printing

[sam wang <stwang@clemson.edu>]

Max,

Are you trying to come up with an emulsion to coat silkscreen? If so,  
the simplest is to just use gelatin. Knox from your supermarket works  
fine. It is colorless, so you might want to wipe on some food dye  
after it's developed to make it easier to see and register. Gelatin  
emulsion can be easily removed with household bleach.

For silkscreen you need an emulsion that's either blocking or not  
blocking, so gelatin is ideal. I have never tried using gum but I  
suspect it would not work well.

I have always wondered about the sensitizer in Diazo emulsions but are  
you sure it's potassium dichromate?

By the way, plain gelatin as silkscreen emulsion worked great with oil  
based inks. I've had no experience with water based inks so do not  
know how well it would work.

Hope this helps.

Sam

On Jan 31, 2009, at 2:10 AM, redrocket wrote:

> Greetings!
>
> I have all my gum chemistry, etc. I understand Diazo type photo  
> emulsion is very similar for screen printing. That the sensitizer is  
> plain old Potassium Dichromate. I'd like to experiment. Any ideas  
> the emulsion part is made of? I'm wondering if I could just  
> sensitize some heavier gum solution and coat a screen? Some one  
> alluded to the emulsion being more of a glue. I guess the final step  
> would be a emulsion remover. I'm guessing the sensitized gum  
> hardened on the screen would be impossible to be removed? What ever  
> the base of the Diazo emulsion once hardened, can be dissolved or  
> removed.
>
> So any advice from those with more photo chemistry knowledge would  
> be appreciated.
>
> Sincerely
>
> Max