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gum-arabick, or fenega, to bind them together, 

 and make them flick 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 

 mufl always be underflood of water-colours, or 

 painting and colouring in water. Indigo mufl 

 be ground with gum difTolved in water, and, 

 when well ground, dried in fmall drops, which 

 will be eafily reduced again to a liquid, in fair 

 water, fit for ufe. I have difcovered a fecret 

 relating to purifying indigo, which may be of 

 ufe : make a flrong lye of pot-afh, then break 

 your rock-indigo pretty fmall, 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 j for the lye, 

 and many of the waters after it, will come from 

 it of the colour of very flrong brown beer, while 

 the bluenefs of the indigo is not extraded ; the 

 foul colour is drawn from the rotten leaves that 

 are mafhed with the indigo when it is made up : 



—it 



