( 214 ) 
Red, Blue and Yellow, compounded all together, in different Proportions, produce all 
the different Degrees of Browns and Cloth-Colours, and a Shadow for White itfelf: 
For if you take a round Piece of Card-Paper, and divide it into three Parts, by Lines 
from the Center to the Circumference, and wafh thefe three Parts with the three 
Primary Colours, fo that neither of them be too ftrong for the other, and all of them 
pretty light, then fix a Pin in the Center, and turn it about fwiftly, you will find the 
Colours will be loft in each other, and the Paper will appear White, though not of 
fo pure a White as before it was coloured. 
Though all Colours may be compounded from three of the principal Colours, yet 
as the Colour-Shops produce a long Lift of Colours, wherein are Variety of Reds, 
Blues and Yellows, of different Shades and Cafts, as well as Browns of many diffe¬ 
rent Sorts, it will be convenient for thofe who fet out in Painting or Colouring, to 
be furnifhed with all of them, which may fave fome Trouble in Com¬ 
pounding. 
I fhall give here a few Hints on the Preparing of Colours, though this SubjeCt has 
been largely handled already.—Common Reafon will teach one to reduce all hard 
Subftances by grinding them well on a Stone, and after grinding them, to levigate 
them finely in Water, by pouring them feveral Times out of one Veffel into ano¬ 
ther, after ftirring them, and letting the gritty and groffer Parts fettle: This not only 
takes out all the gritty and grofs Particles, but frees many Earthy and Mineral 
Colours from corrofive Salts, which would have a bad EffeCt, by making a Work 
fpotty, or changing the Colours, as well as attracting Moifture, which in Time is 
apt to rot the Canvas or Paper on which they are laid. 
There are fome few Colours which are only Gums; thefe are Gamboge and Sap- 
Green : They hold themfelves on the Paper without any additional Gurrij but all 
the Mineral, or Earthy Colours, muft be mixed with a due Proportion of Gum- 
Arabick, or Senega, to bind them together, and make them ftick to the Paper. If 
there be too little Gum, the Colours will rub off if you pafs your Finger over the 
Paper when dried: If too much, the Colours will fhine, crack when very dry, 
and fometimes peel off. What I fay muft always be underftood ofWater-Colours, or 
Painting and Colouring in Water. Indigo muft be ground with Gum diffolved in 
Water, and, when well ground, dried in finall Drops, which will be eafily reduced 
again to a Liquid, in fair Water, fit for Ule. I have difcovered a Secret relating to 
purifying Indigo, which may be of Ufe : Make a very ftrong Lye of Pot-Afh, then 
break yopr Rock-Indigo pretty final], and put it into the Lye, fo that it be covered : 
It may ftand a Month or more. When you pour off the Lye, cover it with boiling 
Water, fhifting it every Day till the Water comes from it pretty clear, and it will be 
purified from all its Filth ; for the Lye, and many of the Waters after it, will 
come from it of the Colour of very ftrong Brown Beer, while the Bluenefs of the 
Indigo is not extracted; the Foul-Colour is drawn from the rotten Leaves that are 
mafhed with the Indigo when it is made up: — It fhould be thus prepared be¬ 
fore the Grinding. 
Vol. IV. 
There 
