Dictionarium polygraphicum. Rocaille.

Dictionarium Polygraphicum:
Or, The Whole Body of Arts Regularly Digested.
Vol II.
London: Printed for C. Hitch and C. Davis in Pater-noster Row, and S. Austen in St. Paul's Church Yard. MDCCXXXV.
1735
ROCAILLE is those green and yellow grains, of which beads are made; which are worn by country girls, and great quantities of which are exported to Africa and other foreign parts, and worn by the negroes, &c. as necklaces, bracelets, &c.

This is used in painting on enamel or glass very frequently tho'it be ill qualified and full of impure lead. Therefore you must chuse the most clear and transparent rocaille, and such as is least charged with colour; yet still this is very far from being so fit for the uses as it should be.

And therefore it will be better in enamel, to use the crystalline matter made with SATURNUS GLORIFICATUS (which see.) However, I shall give the preparation of Rocaille, and how to compound it.

To make the yellow grains, you must take a pound of fine white sand, and three pound of minium, mix and pound them together very well in a mortar, and put the whole into a strong crucible, covered and luted; dry the lute, and set it afterwards into a glass-house or wind-furnace, where the fire is violent, to reduce this matter into glass. Having thus finish'd the Rocaille, make it up either into grains, or any other shape you please.

The method of making the green is quite contrary to that of the yellow: for this put three pound of fine white land to every pound of minium, and it will be very compact.

This stuff will alter its colour, and become a pale red in melting; and these are the compositions and way of making this Rocaille, which is us'd by most workmen. Thus you see there is no preparing it without lead, which renders it so full ot impurity.