Gum Bichromate printing

[stephen_gray98]

Hello.

I am trying to price up chemicals for the gum bichromate process and can't find a supplier of Ammonium or Potassium Bichromate here in the UK. I've tried Silverprint but they do not list it. Any ideas ?

Regards

Stephen Gray

[Mike Wilde]

US based Bostick & Sullivan.

I lucked into a pound jar of ammonium dichromate as a part of an old darkroom lot I bought at a church rummage sale for $10 last spring.

[holmburgers]

I don't know about the restrictions in the UK for dichromates, but I don't think it's good.

Surprisingly, I'd look on eBay. I remember seeing a 10 pound bag for like $20, no foolin'. That's basically a life-time supply I would have to think.

[vyshemirsky]

I called Silverprint last week and they told me that they can't sell any ammonium dichromate due to new harmful material regulations.
I still have about 20 grams of AD, but I don't really know what to do once I run out.

I found that Camlab sell ammonium dichromate, but I have no idea how difficult it is going to be to order from them. I am going to try ordering from Camlab together with some laboratory glassware later this year.

[holmburgers]

This might be a slightly odd suggestion, but this trend of dichromates becoming harder and harder to get is not going to reverse, and I suspect it will make its way to the US someday as well.

With that in mind, I think that alt-printers need to start exploring the use of diazo sensitizers. These are non-toxic and have similar properties to dichromates. As far as I know, they are easy to get everywhere.

Many screen-printing companies make such a sensitizer, and they have been used successfully in carbon systems, notably the UltraStable Permament Color system.

Just a thought...

[paul_c5x4]

There are a few industrial suppliers in the UK that will sell Potassium Dichromate. However, they usually require a trade account, VAT number, and a whole host of other paperwork when it comes to these toxic chemicals. The shipping charges are also disproportionally high when you only want 100g or so (assuming they will sell such small quantities).

I recently purchased some p.dichromate, but had to get 500g as it was the smallest pack available - Way more than I need for the forseeable future. I could be persuaded to trade some, but can not send the stuff in the post, and I suspect the likes of UPS/DHL won't ship either.

[vyshemirsky]

...and they have been used successfully in carbon systems, notably the UltraStable Permament Color system...

Frankly, UltraStable was a proprietary recipe and I have never heard of any other successful applications of diazo sensitiser in carbon printing. On the other hand dichromates are well known to work.

[holmburgers]

Frankly, UltraStable was a proprietary recipe and I have never heard of any other successful applications of diazo sensitiser in carbon printing. On the other hand dichromates are well known to work.

Have you heard of any unsuccessful applications of diazo sensitizer in carbon? I've heard of one, and it happened about 2 weeks ago here on APUG (gmikol). Other than that, I don't know if anyone is even investigating it and that's my point.

[stephen_gray98]

Thanks for all the info. I'm going to get the Fotospeed kit which can be refilled until I'm sure I've got the process and will then look to purchase the separate chemicals later. There is some on ebay (from Japan via Korea !) and there are some companies that will sell it. The ebay item is £25 for 500g post free.

Regards

Stephen Gray

[holmburgers]

What exactly is in the Fotospeed Kit? I'm not able to find a good 'contents list'.