Stiffening.—Stoviog finished, the hats are ready for "stiffening,' a process requiring great study to produce good results. Each hood should he carefully examined, to discover any very thin ones' that may have escaped notice. Should any be found extra light, additional stiffening will make up for it, if noticed in time ; but quantities of goods are hopelessly spoiled through careless examina tion at this stage. The mixtures used for the stiffening process vary according to the taste and experience of the maker, and the class of work he happens to be engaged upon. The mixtures here given will be found perfectly safe, if worked as directed. A number of large tubs, and several dipping-vats will be required for the operation. The first apparatus used will be a steam-chest, Fig. 818, for reducing the " proof." This chest is double-jacketed, for the admission of steam to the interior. The inner part A fits into the outer, the joints being made good with iron-turnings and sal ammoniac, and the rim bolted on as shown. The tap at the bottom is useful for letting off condensed steam, accumulation of liquid in the jacket or steam apace preventing the contents of the pan from being 'brought to the boiling-point. The ground floor is the most suitable place for establishing this apparatus, as it often happens, through carelessness, that the proof or stiffening preparations boil over. Much water is also required in this department, causing inconvenience if it has to be carried up stairs. It is impossible to insist too strongly upon the great importance of thorough study of the art of proofing, as upon it most largely depends the success and reputation of the manufacturer. A perfect knowledge of the nature of the materials is indispensable, while special chemical knowledge will more than repay any student who directs his attention to it. The complete ignorance of the workmen upon whom may depend the success or destruction of perhaps 1000 doz. hats a week, renders it imperative upon the manufacturer to master the details of the process. It will suffice here to describe the important outlines, which, if followed, will at all events conduct to a satisfactory termination the proofing of the soft and hard felt hats that form the bulk of the general home and shipping trades.
The first to be considered is the mixing of what is known as a "water-proof," for the stiffening of the common and medium woollen hats, intended to be of a black colour. Steam is turned into the proof-pan. The workman then weighs out 8 lb. rosin of good quality, 6 lb. gum "thus" (naturally solidified turpentine), 3 lb. borax, and 1 lb. soda. The borax is first dissolved in warm water in the steam-pan, and the rosin, thus, and soda, are then added. When these are quite dissolved, 30 lb. shellac (good " garnet " or " button " will do) is added, and the whole is allowed to dissolve, being kept well stirred to prevent it adhering in lumps to the bottom of the pan. Special observation is needed to note the change in colour. A little experience will aeon teach when to add warm water, which is done at first in small quantities, without relaxing the constant agitation of the compound. A gradual reduction is made in the temperature of the water poured in, until cold water is received by the shellac without chilling it. The strength required will enable the workman to judge of the thickness of the mixture, for water should be added until it is within a few degrees, by Twaddel's hydrometer, of the strength required to proof the brim of the hat, this being the strongest part. " Letting-down " the proof by water after this first process does much damage to it ; the grains of shellac resisting combination with the water, only a partial agglomeration takes place. A microscopical examination of the mixture in the two states, the one just as it is let down in the steam-pan, and the other after being let down with water, will show that the latter, instead of being perfectly mixed with the body of shellac, is only partially held in solution. The fact that this second mixture may proof the brims and crowns of the bats to
the right degree, as shown by the gaoge, is not sufficient ; the hats may be completely ruined never theless. The secret of this lies in the fact that what ought to have formed strength will have evaporated in the stove, leaving the damaged shellac incapable of performing its office. When completed, the workman can test whether the mixture is good, by rubbing it between his thumb and finger : if sound, it will slip between them like glass ; whereas if broken by being chilled too quickly, the feeling will he gritty, and much like that of fine sand. A large, shallow vat must he provided before commencing the process. By placing across this a slab of wood, ou which to fix a fine sieve, the proof can be emptied from the steam-pan, run through this sieve, and left until quite cold before using. As the wool bodies left in the stove are brought to the proofing-room, they should be allowed to cool thoroughly before being subjected to the proof. The "dip," reduced to the right gauge, is contained in a vessel shown in Fig. 819. Some hats require 60° Tw. in the brim, and 30° Tw. in the crown. To manipulate the hats rapidly, two stools of this description are indis pensable. The operator, standing at A, dips the hat into the vessel D containing the proof, or "stiff," as it is frequently designated, sufficiently deep to include the entire brim. When finished, he lays the hat on the slab C, and draws off the super fluous stiffening by a strip of boxwood, about 1 in. thick at one end, and tapered down to a blunt edge on the other, and called a "draw-block," avoiding too heavy a pressure. On immersing the brim again, sufficient stiffening is imbibed, and the hats are taken into the stove, first reversing the folded edges. The draw-block removes any undue stiffening that may have been at tached, and thus secures an even coating. The hat is then passed to the next stool, where the operator thrusts u short, stout stick into the inside of the hood, and plunges the hat bodily into the " crown " proof. Here it is saturated inside and out, giving a little time for it to absorb the preparation, after which it is withdrawn upon the stool, and all the superfluous stiffening is drawn off, as in the first process, and runs back into the dipping pan. The hood is rubbed on all sides with the bare hand, to destroy any patches of thick proof that might have escaped notice. Opening the broad side of the hood, and holding it by the crown, it is laid on the floor to set hard. So soon as the operator has accumulated a dozen, he rapidly sets them in the steamer for 20 minutes, and afterwards in the hot stove, for 60 minutes, to sharply fix the proof, removing them into the air afterwards to 000l. They are then again ready for the steaming-chest. Before proceeding to explain this process, it will be necessary to follow fine goods through the proofing department, as well as soft hats. In all dip proofs where the steam-pun is used, warm water can be employed to dissolve the borax, and this must always be the first process, before adding the gum thus and rosin. For a mixing of soft proof, weigh out 4 lb. borax, dissolved first in warm water, 3 lb. rosin, and 3 lb. gum thus ; dissolving this, add 30 lb. shellac ; keeping the mixture well stirred, 1 pint linseed oil will be mixed in, pouring in a little warm water first, and " breaking " the shellac gradually until cold water can be added. Having brought it to the required strength, it is poured into a vat, kept for the purpose, for a couple of days before using, as it works much better after standing. The strength, measured by hydrometer, must be left to the judgment of the maker, for the felt for this class of hat is made of so many strengths that, while some require scarcely any stiffness, others need 5-10° Tw. in the brim—less in the crown, as it is to he more pliant.