A solution of shell lac in water & liq ammonia may be used instead of size to rub down the threads of the canvass with, and when dry the threads do not swell by using any watery mixture because the solution of lac is not soluble when it is dry – ,The ammonia evaporating must, I should think leave the lac in a pure state so that the canvass threads might be further smoothed down by the application of heat, perhaps by pressing the cloth through rollers heated by gas or steam perhaps simply wetting canvass with the solution, then letting it dry & passing it through the hot rollers, with some kind of straining contrivance to pull it out to its full tension before the heat sets it If this could be done it would be an important step towards preparing canvass by machinery ,