Penland Additive Formulas for 19 pounds of batch. (Dave Bross noted: I think this may be wrong, seems like an awful lot of colorant for 20# of batch on some of these)
Recall that "bone ash" in these is for a specific phosphate source that is no longer available (Bone Ash 21). I found Bone Ash on Amazon and other sources but I worry that it's just not the same. Besides, true bone ash would have loads of calcium which Dave Bross found negatively impacted melting an opal phosphate glass. I would suggest substituting a pure phosphate such as sodium tripolyphosphate (STP, STPP).
The soda ash add back is important as SP color base has a subtraction of 1.7lbs soda nitrate for every 98 lbs of batch (Kenny Pieper). The nitrate is removed to prevent oxidation in the glass.
No Melting instructions are included. Dave suggests using the colorant percentages to make colored versions of your own glass batch formula. As I move on to different colors I'll be trying and discussing the details of making these successfully.
A note on Mixing: SP color base must be mixed before using. So...you have to have a way of completely mixing up 100lbs of batch before getting started. For the colorants, add them into a separate container and mix completely before adding into the base. Try dumping a little batch into a bucket and a little colorant...mix. Repeat until all ingredients are in the bucket and then mix again...a lot (Drill with paddle bit or whatever works for you).
· Purple: 200g mang dioxide, 90g soda ash.
· Opal Purple: 70g mang dioxide, 15g cobalt carb, 450g bone ash, 95g soda ash.
· Violet: 150g mang dioxide, 5 10g cobalt carb, 65g soda ash.
· Opal Yellow: 110g cadmium sulfide, 20g sulfer, 650g zinc oxide, 70g. pot ash, 90g soda ash.
· Yellow: 128g cadmium sulfide, 660g zinc oxide, 68g pot ash, 95g soda ash.
· Yellow Orange (for 18lbs): 40g selenium, 650g zinc oxide, 110g cadmium sulfide, 140g pot ash.
· Opal Green: 50g potassium dichromate, 20g black copper oxide, 450g bone ash, 85g soda ash.
· Opal Green 2: 25g potassium dichromate, 10g black copper oxide, 90g borax.
· Opal Jade: 40g black copper oxide, 20g potassium dichromate, 450g bone ash, 95g soda ash.
· Turquoise: 200g copper carb, 55g potassium dichromate, 95g soda ash.
· Blue: 200g copper carb, 7g cobalt carb, 25g potassium dichromate, 90g soda ash.
· Med Dark Blue: 150g black copper oxide, 90g soda ash.
· Opal Dark Copper Blue: 240g black copper oxide, 405g bone ash, 90g soda ash.
· Lapis: 50g cobalt carb, 180g borax.
· Opal Lapis: 30g cobalt carb, 10g black copper carb, 450 bone ash, 85g soda ash.
· Opal Red: 128g cadmium sulfide, 64g powdered selenium, 600g zinc oxide, 68g pot
ash. 430g bone ash, 430g bone ash, 95g soda ash. To darken, add 72g selenium, 90g pot ash.
· Pink (18lbs): 40g selenium, 90g cadmium sulfide, 600g zinc oxide, 68g pot ash, 80g soda ash.
· Black: 231 mang dioxide, 11g potassium dichromate, 32g cobalt carb, 118g black
nickel oxide.
