108 - A Yellow Lake from Broom Flowers, for Paint
Make a batch of lye from glassmaking soda and lime, and make it reasonably strong. In this lye, boil fresh broom flowers over a slow fire until the lye draws out all the tincture of the flowers.
You will know this [state] when you take the flowers out and see that they have turned white, and become thoroughly uncoloured, and the lye is as yellow as a fine Trebbiano wine.
Now take out all the flowers, and put the lye in glazed earthen pots over the fire, so the lye boils. Into this add as much roche alum as can be dissolved with the fire, then remove it, and empty the lye into a vessel of clear water. The yellow colour will settle to the bottom. Leave it to rest, and then decant off all the water. Again, pour more fresh water over it, decant again, and let it rest. As before, the dye will go to the bottom. This way, you will extract all the lye salts and the dose of alum out of the dye.
Take note that the more you wash this dye of the lye salts and alum, the more beautiful it will become, and more lovely in color. Always wash it with common water, which will carry
away the lye salts and the alum, hand in hand.
First, decant the water, and then leave it until the yellow dye settles to the bottom. Repeat this until the water tastes sweet without saltiness. When you notice this, it will be the sign that the water has washed away all the salt and alum. The pure and beautiful lake will remain in the bottom. Drain it well from the water, and while still damp spread it over pieces of white linen, and leave it to dry over newly baked tiles. Let it dry in the shade, and you will have a beautiful yellow coloured Iake for the painters and for glass as well.