SECTION VIII.
Of the manner of laying on and burning the enamel colours.
THE colours being prepared, us above directed, and reduced to powder by due levigation, and waffling over where they are required to be extremely fine and there is no unvitrified fait in the mixture, they mu ft be tempered on a China or Dutch tile with oil of fpike or lavender, to which moft artifts add likewife oil of turpentine j and fome (but I think errone- oufly, as I have before mentioned) a little linfeed or olive oil j and then ufed as paint of any o- ' fher kind. But it fhould be avoided to mix more of the colours with the efiential oils than will be immediately ufed 5 becaufe they dry away extremely faft, and would not only be wafted, but give a cohefion to the particles of the colours, that would make them work lefs freely when again diluted with the oil.
The colours being thus laid on the pieces to be painted, the proceeding muft be in all re- fpeCts the fame as with die grounds, in whatever manner they are to be burnt, either in the muffles or coffins; but greater nicety muft be obferved with relpeCt to die fire j asrthe effects of any error in that point are of much greater confequen.ce^n the burning the colours than grounds} efpecially- if the white of the grounds be formed from the calx of tin or antimony } and not arfenic. '
Pit coal, as was above obferved, may be employed for burning as well the colours as the grounds, where the muffle or coffins are ufcd; or any other method perfued that wholly hinders the fmoke and fumes from having any accefs to the enamel.