The number and variety of sizing substances render it impossible to adequately describe the properties and use of each. Mention is only made of those of greatest use and importance; yet the list is sufficiently long. They may be divided into four classes--those for forming the basis or body of the mixing or adhesive substances, those for rendering the dried size pliable, weight-giving substances, and antiseptics. In the adhesive substances, _flour_ is of first importance for medium and heavy sizing. This is manufactured by grinding a portion of the wheat grain, and the qualities used in sizing are of the better sort, fully equal to those used for bread-making. For giving body and adhesiveness to the size, flour is valued, but is found a rather expensive substance, and rather inclined to mildew. To remove this latter disadvantage, and also to render flour more suitable for the purpose for which it is intended, most manufacturers steep it in water for periods varying from three days to as many months. Practical men and sizing specialists generally agree, however, that from two to three weeks is the best length of time for fermentation. On judging the quality of flour, comparisons of colour and stiffness after boiling are made; in the latter case equal quantities of each sample should be taken and treated similarly, both as to amount of water taken and time allowed for boiling. The best test, however, and one that applies to all sizing substances, is whether it “goes far” or not in actual use. _Farina_ is the ground starch of the potato, and largely used in light sizing on account of its cheapness and convenience for mixing. It requires the use of a softener with it, generally tallow or wax, to counteract a harshness which it gives to the twist when used alone. Two other vegetable substances--sago and rice flours--are used for very light sizing, especially for fine reeds or coloured work. _Softeners._--Unless some ingredient with a more or less greasy nature be mixed with the above substances in sufficient quantities, the warp is so brittle and harsh as to break frequently in the loom. The substance most frequently used is tallow (refined animal fats). This is somewhat expensive, yet its softening properties in heavy sizing are often introduced into the mixing. The quantity of tallow to each bag of flour or clay varies according to the quantity of other softeners used. In using tallow care must be taken to obtain it hard and free from grit; much wear of clacks and rams may be attributed to gritty matter in this and other ingredients, especially in china clay.