Glue

Glue is prepared from waste pieces of skin, horns, hoofs, and other animal offal. These are steeped, washed, boiled, strained, melted, reboiled and cast into square cakes, which are then dried. The strongest kind of glue is made from the hides of oxen; that from the bones and sinews is weaker. The older the animal, the stronger the glue. Good glue should be hard in the cake, of a strong, dark color almost transparent, free from black or cloudy spots, and with little or no smell. The best sorts are transparent and of a clear amber color. Inferior kinds are sometimes contaminated with the lime used for removing the hair from the skins of which they are made. The best glue swells considerably (the more the better) when immersed in cold water, but does not dissolve. ;md returns to its former size when dry. Inferior glue made from bones, will, however, dissolve almost entirely in cold water.

How To Prepare Glue

To prepare glue for use it should be broken up into small pieces, and soaked in as much cold water as will cover it, for about twelve hours. It should then be melted in a double glue pot, covered to keep the glue from dirt. Care must be taken to keep the outer vessel full of water so that the glue shall not burn, or be brought to a temperature higher than that of boiling water. The glue is allowed to simmer for two or three hour-, then gradually melted, so much hot water being added as will make it liquid enough, just to run off a brush in a continuous stream, without breaking into drops. When the glue is done with, some boiling water should be added to make it very thin before it is put away. Freshly made glue is stronger than that which has been repeatedly melted. Too large a quantity should not therefore be made at a time. Glue may be freed from the foreign animal matter generally in it by softening it in cold water, washing it with the same several times till it no longer gives out any color, then bruising it with the hand, and suspending it in a linen bag beneath the surface of a large quantity of water at 66° Fahr. By doing this the pure glue is retained in the bag, and the soluble impurities pass through. If the softened glue be heated to 122° without water, and filtered, some other impurities will be retained by the filter, and a colorless solution of glue be obtained.

The addition of a little bichromate of potash will render glue impervious to moisture after exposing to the light, and a small quantity of methylated spirits will greatly improve its keeping qualities.

Mixing Glue

A minimum amount of glue should be used in good work, and it should be applied as hot as possible. The surfaces of the wood to be united should be clean, dry and true: they should be brought together as tightly as possible, so that the superfluous glue is squeezed out. The cohesion of a piece of solid glue, or the force required to separate one square inch, is four thousand pounds. The strength of common glue for coarse work is increased by the addition of a little powdered chalk. The hotter the glue/the greater its cohesion; therefore in all large and long joints the glue should be applied immediately after boiling. Glue loses much of its strength by frequent re-melting; that glue therefore, which is newly made, is much preferable to that which has been re-boiled.

Glue-Pot

A glue-pot recently perfected consists of a circular kerosene lamp, made of tin, resting upon a tin bottom 8 ½ inches in diameter. The lamp is fitted with a tin chimney in place of glass, and fitted with a small aperture, covered with mica, so as to see how to regulate the flame. The glue pot is made of copper, tinned on the inside and supported upon a rim setting up about six inches from the bottom of the lamp, the rim supported by three legs, soldered and riveted to the rim and bottom of lamp rest. The pot in which the bottom is placed has a portion of the bottom arched, to give more heating surface, and connecting with the chamber under the pot is a flue, passing out and up alongside of the pot which carries off any smoke from the lamp, and also acts as a draft to the flame. This pot is five inches in diameter, and about six inches high. The pot for the reception of the glue is set in the same as an ordinary glue pot, and will hold about a quart of glue. The whole can be carried to any place where you wish to use it, and still have the heat kept up. The cost of oil is but a few cents a week.

Another improvement is in the pot being of copper, tinned. It will not corrode and spoil the glue, as is the case with iron.

French cabinet-makers use a glue-pot with an inside pan made of glazed earthenware and divided radially into three divisions, in one of which is kept strong glue, in another weaker, and in the third water only, with a brush or piece of sponge for cleaning off superfluous glue from the work.

A few holes bored near the top of the inner vessel of a gluepot, by admitting steam from the outer vessel will prevent the glue from solidifying on the side. They need not be bored round the whole circumference of the pot, to allow of pouring out the glue if necessary.

How To Prevent Glue Cracking

Glue frequently cracks because of the dryness of the air in rooms warmed by stoves. The addition of chloride of calcium to glue will prevent this disagreeable property of cracking. Chloride of calcium is such a deliquescent salt that it attracts enough moisture to prevent the glue from cracking. Glue thus prepared will adhere to glass, metal, etc., and can be used for putting on labels without danger of their dropping off.

Strong Glue To Resist Moisture

Dissolve gum-sandarac and mastic, of each a quarter of an ounce, in a quarter of a pint of spirits of wine, to which add a quarter of an ounce of clear turpentine: now take strong glue, or that in which isinglass has been dissolved; then, putting the gums into a double glue-pot, add by degrees the glue,constantly stirring it over the fire till the whole is well incorporated: strain it through a cloth, and it is ready for use. You may now return it to the glue-pot, and add half an ounce of very finely-powdered glass; use it quite hot. If you join two pieces of wood together with it, you may, when perfectly hard and dry, immerse it in water, and the joint will not, separate.

Glue To Resist Moisture

To two quarts of skimmed milk add half a pound of the best glue; melt them together, taking care they do not boil over, and you will have a very strong glue, which will resist damp or moisture.

Portable Glue

Boil one pound of the best glue,strain it very clear; boil also four ounces of isinglass; put it into a double glue-pot, with half a pound of fine brown sugar, and boil it pretty thick; then pour it into plates or moulds. When cold you may cut. and dry them for the pocket.

This glue is very useful to draughtsmen, architects, etc., as it immediately dilutes in warm water, and fastens the paper without the process of dampening: or, it may be used by softening it in the mouth, and applying it to the paper.