127 - A Glass as Red as Blood, That Can Serve as Rosichiero
Melt 6 lbs of lead glass, and 10 lbs of crystal frit in a crucible. When it clarifies, throw it into water, return it to the crucible, and leave it to clarify thoroughly. When it has clarified well, add calcined red copper to this glass, for example 4 or even 6 oz.
Leave it to simmer and clarify thoroughly, then add ground red wine tartar. lncorporate it with the glass, leave it to clarify, and look to see if the colour appeals to you. Take a proof, and if you find it insufficiently tinted from the red copper and tartar, make it right. Take another proof, and return it to the heat [strike it), enough so that it becomes very red, this will intensify the colour.