6. It is quite possible to over-bake enamels and spoil the colours, and likewise under-baked enamels will not be tough enough to withstand hard wear. Particular attention should be paid to the directions on the package labels, as the various pigments require different temperatures.
7. Stoving enamels, if left in an opened can, tend to thicken considerably. For this reason, keep the can closed when not actually using the enamel.
For thinning purposes we recommend kerosene. Sp. gr. 810 at 60° F.
8. Ovens should be properly ventilated to allow the proper oxidation necessary in baking.
It has already been pointed out in these pages that the success of painting by dipping, spraying, "flowing on," in fact, all other mechanical means, depends upon the exact properties of the materials used. The same is true with enamels, which are made from a large variety of formulæ so as to dry slowly or quickly in the air, or when subjected to heat in a stove. The author feels he cannot do better than take as a guide to the properties of enamels in general the extremely useful handbook published by Wilkinson, Heywood and Clark, under the head of "Enamels for every Purpose." This book gives practically all the information concerning enamels likely to be required by the average user. The products are divided up under different heads, for example, one page is headed "Heat Resisting and Slow Drying Enamels." These dry fit to handle in 16 hours, and dry bone hard in 24 hours. They are made to withstand heat up to 212° F., and for this reason are suitable for enamelling iron baths, radiators, etc., particularly so as to effectively resist hot water without softening or peeling. They are made in a number of beautiful colours. A somewhat similar series of enamels is made which dry quicker, viz., in 8 hours fit to handle and quite hard in 12 hours. They are useful for touching up radiators, stoves, steam pipes, etc., and are made in white and a dozen or more colours. The next series which demands our attention are "Dipping Air Drying Enamels." They dry in 8 hours and are quite hard in 12 hours. They are claimed to produce a finish equal to that obtained by a quick air drying brushing enamel with the labour of brushing eliminated. For a finish done by immersing the article to be painted these are capital enamels, but they require to be used with a stirrer of some sort in the tank.