Dictionarium polygraphicum. Blue Japan.

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
1. Take gum water, what quantity you please, and of white lead a sufficient quantity, grind them well upon a marble, take Ising-glass size, what quantity you please, and of the finest and best smalt a sufficient quantity; mix them well together, then add to them of the white lead ground (as before) to much as will give it a sufficient body, mix all together to the consistence of a paint.

2. Do your work over with this mixture 3 or 4 times, till you perceive the blue to lie with a good and fair body, letting it dry thoroughly between each time; if your blue is too pale, put more malt among your size, without any white lead.

3. Then rush it over smooth, and go over it again with a stronger blue, and when it is thoroughly dry, wash it 3 times over with the clearest ising-glass size alone; and let it stand for 2 days to dry, covering it.

4. Then warm your work gently at the fire, and with a pencil varnish your work over with the finest white varnish, repeating'it 7 or 8 times, letting it stand to dry 2 days, as before. After which, repeat again the third time the washes 7 or 8 times in like manner.

5. Let it now stand to dry for a Week, and then polish it as before directed, and clear it up with lamp-black and oil, to give it a polite and glossy appearance.

6. As to the colour, you must be guided by your reason and fancy, whether you will have it light or deep; for a small proportion of the lead makes it deep; a greater, light.
Also the size for laying whites, blues, or any other colour, ought not to be too strong, rather weaker, and just sufficient to bind the colours, and make them stick on the work; for if it be too stiff, it will be apt to crack and fly off.
And the reason of washing twice with clear size, is to keep the varnish from sinking into, or tarpishing the colours; and in this case it ought to be of a strong and full body.