This method well merits close study, especially as at present workmen often so far follow the traditions of their craft as to lose sight of such points of special advantage as might easily be grasped if tradition were allowed to give way more freely to thought and experiment.
The page of type, or " forme," which is to be moulded, instead of being locked up in the chase surrounded with the ordinary wooden furniture, has a type-high border about 3/8 in. wide around it; but the face of this type-high border does not come quite close up to the type, there being a space of 1/8 in. between them. This type-high border is ordinarily obtained by surrounding the forme with strips of type-metal called "clumps," or •' stereo - clumps," these clumps being type high, and about 1/2 in. wide; but a bevel on the edge placed next to the type reduces the face-width to about 3/8 in., and gives the clear space of about 1/8 in. or so between the face of the clump and the type. The object of the clumps is to form a level bed for the strips of metal - commonly called "gauges" - which determine the thickness of the plate. The space between the type and the face of the clump leaves room for the saw-cut if the plate is to be trimmed close, or for the bevel if the plate is to be trimmed for mounting with catches on a metal block.
Now the forme should be planed level, not too tightly locked up, and its face must be slightly but completely oiled, this being done by rubbing it with a flat brush, not too heavily charged with oil, the brush being about as stiff as an ordinary hat brush. The traditions of the trade ordain that the oil should be the finest olive oil; but as a matter of fact, neither olive oil nor cotton-seed oil, which is now commonly sold as olive oil, is the most suitable, as these oils - and more especially the latter - are saponified very readily by any trace of alkali which may remain on the forme. A much more suitable oil is the very thin mineral lubricating oil which is sold retail at Is. 6d. a gal. Here is a case in which an article sold at the lowest price is the best, and in connection with stereotyping - as indeed with most industries - there are many such cases; so much so that one must look with suspicion on the common but vague instruction to " use only the very best materials." The practical interpretation of this is to use just those samples for which the shopkeeper chooses to charge the highest prices; and when such an instruction is given as generally applying to all materials used in a craft, one may, perhaps, reasonably suppose that it is given because the instructor's knowledge of the materials is too uncertain for him to specify what qualities are desirable.
We now come to a very important matter: the flong and the materials used in its preparation. First, let us take the paste used to cement the various layers of paper together, and as to this matter one finds in the usual instructions merely a confusing crowd of recipes without the smallest indication as to -choice between them, and some of these recipes order the use of materials the special service of which it is very difficult to conjecture.
As an adhesive, ordinary gum (arabic or acacia gum) is undesirable; it penetrates the substance of the paper, tends to make it unmanageably hard and brittle when dry, and, weight for weight, it gives less adhesion between sheet and sheet than is the case with starch or flour paste. Gum is specially bad in relation to the fine tissue which forms the face of the flong, as in penetrating this it not only tends to adhesion with the type, but where the gum has penetrated the face of the cast obtained will have a rougher texture than elsewhere. In addition, gum is expensive, and, what is perhaps worse, very variable in quality.
Starch paste is a very good adhesive, as its water principally penetrates the sheets, leaving the starch where most wanted, and that sponginess, which is a characteristic of good and useful flong, is retained.
Good as simple starch paste is, a paste made from a moderately glutinous flour, such as wheat flour, is better, as the gluten gives the starch greater consistency and adhesiveness without other disadvantages. Moreover, wheat flour paste is easier to prepare and to manipulate than starch paste, and, if measured by adhesive power, is very much cheaper. Besides, it penetrates the paper even less than starch paste. Altogether the advantage rests with wheat flour paste as the main adhesive.
Glue (the term includes gelatines and sizes) by itself is not a very suitable or desirable adhesive to use, as it is subject to the same disadvantage as gum arabic as regards penetration of the paper, yet in a lesser degree; but when used in conjunction with sufficient flour paste, the penetrating quality is eliminated, and owing to the setting of the glue the flong acquires increased sponginess, and also the valuable quality of being more rapidly compressed by the face of the type when the metal is warm, as the glue melts and consolidates the compressed parts. In addition, by the use of glue along with flour paste, the flong becomes capable of holding rather more water without becoming flabby, and where the flong is not compressed, it dries more spongy than would otherwise be the case. There is advantage in using glue with the paste, whether the type is to be moulded cold or warm, but very especial advantage in the latter case. The sort of glue most suitable is the soft and degenerate glue sold retail in the oilshops at 4d. per lb., high-priced hard glues and fine gelatines being very much less suitable.
Instead of using glue, it saves time to purchase size, but care should be taken to use the low-priced size sold as common size (14 lb. for 1s. in London oilshops), and not the harder and finer size known as "patent size."