cadmium colors in contact with lead based glasses

[Pete VanderLaan]

I'll start his with this simple observation: If anyone ever wondered why Cadmium yellows and reds turn a sort of ugly brown in contact with a lead based color, they do not like each other. Cad sels are not made using lead. Nominally, they're Zinc/Potash glasses. It's the main reason they are so intolerant of many clear glass bodies.

Further, any cadmium glasses in the presence of copper based colors, leaded or not will turn a really dirty brown as well.

Now do what you will with this board.

[Steven O'Day]

Fusers consider this a feature:
http://www.bullseyeglass.com/images/...seye_glass.pdf

[Kenny Pieper]

When I make cane with my stiff white that has lead in it and want to cover it with either red of a sulfur amber I have to put a layer of clear in-between or it will turn dark brown.
I am sure this will also be true if using the gaffer duro. Many colors will not work if touching.

[Pete VanderLaan]

It's an anti-feature

[Will Robertson]

Originally Posted by Pete VanderLaan

Cadmium yellows and reds turn a sort of ugly brown in contact with a lead based color, they do not like each other.

Further, any cadmium glasses in the presence of copper based colors, leaded or not will turn a really dirty brown as well.

This is very important information and not documented in many of the books - interestingly it is documented in the pages of the Portland Mercury - a useful source of inside information for anyone interested in coloured glass-making:

"It would be next to impossible to switch cadmium and lead in and out of the same furnace," says Eric Miller, a Portland designer who earlier in his career worked for both Bullseye and as a batch formulator for North Portland's Uroboros Glass. "Once either one is in a furnace, you're pretty much stuck. Particularly with the lead, since that can precipitate into little nodules in the furnace bricks like cavities in your teeth and turns any cadmium glasses dark brown."

Miller says if you wanted to go back to cadmium production once lead has been in a furnace, you might have to re-line it at a cost of at least $10,000 for even a small furnace.

"Archie," another glass expert who requested anonymity, put it starkly: "Lead can never [be] in a furnace that makes a cadmium yellow or selenium red. It will, for the rest of its days, turn [the glass] shit brown."

https://www.portlandmercury.com/news...-on-toxic-lead