process, so as to obtain a full yield (about 10%) of glycerin, and the
resulting fatty acids then subjected to acid saponification, so as to
get the higher amount of stearine. At the best, however, some 30% of
oleic acid remains, and though often sought, no satisfactory method of
converting this residue into solid has been discovered. It constitutes
"red oil," and is used in soap-making and in woollen manufacture. In the
process patented by Ernst Twitchell in 1898, decomposition is effected
by boiling the fat with half its bulk of water in presence of a reagent
obtained by the action of sulphuric acid on oleic acid and an aromatic
hydrocarbon such as benzene.

The wick is a most important part of a candle, and unless it is of
proper size and texture either too much or too little fuel will be
supplied to the flame, and the candle will gutter or be otherwise
unsatisfactory. The material generally employed is cotton yarn, plaited
or "braided" by machinery, and treated or "pickled" with a solution of
boracic acid, ammonium or potassium nitrate, or other salt. The
tightness of the plaiting varies with the material used for the candle,
wicks for stearine being looser than for paraffin, but tighter than for
wax or spermaceti. The plaited wick is flat and curls over as the candle
burns, and thus the end is kept projecting into the outer part of the
flame where it is consumed, complete combustion being aided by the
pickling process it has undergone. In the old tallow dips the strands of
cotton were merely twisted together, instead of being plaited; wicks
made in this way had no determinate bias towards the outside of the
flame, and thus were not wholly consumed, the result being that there
was apt to be an accumulation of charred matter, which choked the flame
unless removed by periodical "snuffing."

Four ways of making candles may be distinguished--dipping, pouring,
drawing and moulding, the last being that most commonly employed.
_Dipping_ is essentially the same as the domestic process already
described, but the rate of production is increased by mounting a number
of wicks in a series of frames, each of which in turn is brought over
the tallow bath so that its wicks can be dipped. _Pouring_, used in the
case of wax, which cannot well be moulded because it contracts in
cooling and also has a tendency to stick to the moulds, consists in
ladling molten wax upon the wicks suspended from an iron ring. When of
the desired thick