Dictionarium polygraphicum. To extract Lake from BROOM FLOWERs.

Dictionarium Polygraphicum:
Or, The Whole Body of Arts Regularly Digested.
Vol I.
London: Printed for C. Hitch and C. Davis in Pater-noster Row, and S. Austen in St. Paul's Church Yard. MDCCXXXV.
1735
First make a lixivium, or lye of soda of the glass house, and fresh quick lime, which must be pretty strong, in which put in the broom flowers, over a small fire, until all the tincture be drawn from them, the flowers become white, and the lye receive the yellow colour.

Then take out the flowers, and put the lye into a glaz'd earthen vessel to boil, adding thereto as much roch-alum as it can well dissolve; then take it off, and putting it into a large vessel, mix it with fair water, so the yellow will separate and descend to the bottom; let it rest there a little, and afterwards decant the water off gently, and so put in more fresh to it again and again, until the water has drawn off all the salt and alum from the lixivium, and it becomes clear.

Thus the colour will be very well cleans'd of the salt and alum, and remain exceeding fine and bright; spread it on pieces of white linen, and let it dry in the shade on new baked tiles, and you will have a most admirable yellow for painting.