Fig. 1.
There are on the market two sorts of mixing machine for paints that would prove of great service to the painter who has to produce large quantities of paint. But, as a rule, they are only used by paint manufacturers. One known as the vertical mixer, is represented in [Fig. 1], and is suitable for painters’ use. It consists of a cylinder which contains the paint, and in this are three bent knives or scissors. The handle attached, on being operated, turns the cylinder in one direction and the knives in the opposite direction, these knives in the meantime revolving around on their own axes. The paint is thus mixed very quickly, and as the cylinder may be had to hold several gallons, in the case of bridge work, wall work, or other positions where a very large quantity of the same paint is required, the purchase, for a few pounds, of such a machine may mean a saving of a considerable amount of labour. The mixer illustrated is manufactured by Messrs. Torrance & Sons, of Bittern, Glos. In many shops, where large quantities of stone colour and other paints have to be turned out, such a machine would soon repay its cost.
For ordinary quantities of paint, of which white lead forms the base, the following is the method usually employed. It will be understood that the paint consists of a base such as white lead, linseed oil, either raw or boiled, driers—either patent or liquid—and turpentine. A can or kettle is most usually employed for mixing the white lead in, and this is first thinned out and mixed with the driers and oil, the colour being afterwards added to it. A little oil is first placed in the can, which is twisted around so that the oil covers every part of the inside surface. This prevents the lead sticking against the tin. A sufficient quantity of oil and the patent or other driers is then added. The most convenient implement for actually mixing the paint is a broad piece of wood shaped like a narrow spade, or a spatula may be employed. The lead is stirred and beaten against the sides of the tin until the whole is of the same consistency, and more oil is added until the thickness is not sufficient to support the stick standing upright. Turpentine may now be added to further thin the mixture, and then the colour is added. It may be noted here that the result is not so satisfactory if the turpentine is added before the oil. The best way of mixing actual colours is to place them on a stone, thoroughly amalgamating one with the other by means of a spatula. When the colour is what is required it is added to the white. To take a simple case of a gray, a little black would be beaten up on the stone, and when quite thin added to the pot of white. This would then be stirred up thoroughly and the grey colour observed to see whether it was sufficiently dark. Then a very little red and blue might be prepared on the stone and this be added to the pot, the mixture being again stirred. Two very important rules must be observed at this point. The first is that the colours ground in oil should be used and not dry colours. If dry colours are employed oil must be added to them on the stone and not in the pot. We may repeat, by way of emphasis, under no circumstances must dry colours be added to the pot of colour. This is a rule to which there is absolutely no exception. The second rule, and one which is equally important, is to add only a small quantity of colour to the pot of white at the time. Taking the case once more of the grey, a little black being added and the mixture well stirred it can be seen at a glance whether the desired depth of shade is obtained. On the other hand, it would be quite impossible to take any of the black from the mixture, and should it be too dark the only way to lighten it would be to add more white, and this would probably mean mixing much more paint than was required for the job.
The paint having been mixed to the exact colour required, all that now remains is to strain it. A piece of muslin is often used for this purpose, but a far better method is to use a wire gauze strainer, which may be purchased for a small sum and will last for a considerable length of time. The advantage of this in addition to its permanence is that the hard portions of the paint may be beaten against the gauze, and so the waste be reduced to a minimum.
Fig. 2.
Fig. 3.
An excellent shape of paint strainer is that shown in [Fig. 2], which is shown in parts in [Fig. 3]. A, represents the body of the strainer, B, the clips which hold the compression band C, and D, represents the gauze. The advantage of this construction is that the gauze after use may be easily taken out, cleaned and replaced. This strainer or its equivalent should form part of the equipment of every paint shop, large or small.