22 PREPARATION AND MOUNTING 



GOLD SIZE. This substance may always be procured at any 

 colourman's shop. The process of its preparation is long and 

 tedious. It is,\herefore, not necessary to describe it here. Dr. 

 Carpenter says tft^t it is very durable, and may be used with 

 almost any preserv^ke liquids, as it is acted upon by very few 

 of them, turpentine being its only true solvent. If too thin, it 

 may be exposed for awhile to the open air, which by evaporation 

 gradually thickens it. Care must be taken, however, not to ren- 

 der it too thick, as it will then be useless. A small quantity should 

 be kept on hand, as it is much more adhesive when old. 



LIQUID GLUE is another of these cements, which is made by 

 dissolving gum shellac in naphtha in such quantity that it may be 

 of the required consistency. This cement appears to me almost 

 worthless in ordinary work, as its adherence can never be relied 

 upon ; but it is so often used and recommended that an enumera- 

 tion of cements might be deemed incomplete without it. Even 

 when employed simply for varnishing the outside of the glass 

 covers, for appearance' sake alone, it invariably chips. Where, 

 however, oil is used as a preservative liquid, it serves very well to 

 attach the thin glass ; but when this is accomplished, another 

 varnish less liable to " chip " must always be laid upon it. (See 

 Chapter IV.) 



BLACK JAPAN. This is prepared from oil of turpentine, linseed 

 oil, amber, gum anime, and asphalt. It is troublesome to make, 

 and therefore it is much better to procure it at the shops. It is 

 a really good cement, and serves very well to make shallow cells 

 for liquids, as will be described in Chapter IV. The finished cell 

 should be exposed for a short time to the heat of what is usually 

 termed a " cool oven." This renders it very durable, and many 

 very careful manipulators make use of it for their preparations. 



ELECTRICAL CEMENT. This will be found very good for some 

 purposes hereinafter described. To make it melt together 



5 parts of resin. 

 1 " beeswax. 

 1 " red ochre.* 



* Dr. Griffiths says that the addition of 2 parts of Canada balsam renders 

 this cement much more adhesive to the glass. 



