THE final test of a paint brush is to be made only in use over a reasonable period of service, but, at the outset, there are several points which distinguish the good from the inferior brush. The type and quality of hair or bristle employed are of far greater importance than a highly finished and colourful handle. In consequence, it is the hair and its method of attachment which must claim the attention in the selection of a brush. Another consideration is the purpose for which the brush will be used.
Oil paints and varnishes are too viscid to be applied and evenly spread with anything softer than hogs’ hair bristle; there are, however, a number of finishes, chief of which are lacquers, french polish and cellulose lacquers, which require a very soft brush of squirrel, fox, or camel hair. Whatever the type of bristle employed, it is always desirable to select a quality of sufficient springiness to keep its shape during use.
The best paint brushes are made from full length hogs’ hair bristles (previously sorted into equal lengths) which, by reason of their tapering shape, impart a combination of strength together with the fine, soft tips so necessary for good brushwork. Any trimming or cutting of the tips of bristles may form a more shapely brush, but if carried to excess will produce a brush too stiff for anything except the roughest of painting.
Qualities of Hogs’ Hair
These are not very easily distinguished. The creamy-white ‘lily bristles’ are regarded as the best, followed by grey and black, in order of merit. There are, of course, various grades of each type, and while price is usually a good criterion of the quality of any reputable maker’s goods, it is important to discriminate between limp, inferior bristles and those which exhibit the essential charac- teristics of springiness and good shape.
The long bristles employed in the larger types of both paint and distemper brushes are split at the tips into two or three strands. This is a desirable feature as it proves that a genuine full length material has been used. In smaller brushes .this characteristic is not usually evident, but one can easily compare the degree of tapering (or lack of it) by firmly pressing (a) the base, then (b) the tip of a brush, between the finger and thumb: (b) should not be more than half the thickness of (a).
Hogs Hair Substitutes
Both horse hair and vegetable fibre have at times been found intermixed with genuine hogs hair in the cheaper type of imported paint brush. These substitutes are noticeable by (a) their lack of spring; if bent at a sharp angle they usually remain crippled; (b) bristle and horse hair will, when burnt, give off the characteristic smell of burnt hair; vegetable fibre does not; (c) horse hair lacks the tapering shape of bristle and is smoother to the touch.
Vegetable fibre is quite unsuitable for use in paint brushes, and is more usefully employed in brushes intended for the application of caustic solutions such as those used for the removal of varnished wallpaper and the cleaning of stonework, etc.
Vulcanized Rubber Cement
This has for several years been regarded as the most efficient medium for holding the bristles firmly in place. The words ‘Rubber Set’ stamped upon a brush, indicate that not only has this type of adhesive been employed, but that the brush is capable of with- standing the action of oil, water, and any of the solvents normally used in paints and varnishes.
Metal ferrules are of three classes: the machine pressed, seamless type, has a plain band of metal devoid of rivets, being easy to keep clean. This type of brush is ideal for use with varnish and enamel. The more common type is of thinner metal, secured with rivets and nails, and is universally employed for brushes of all sizes. Copper wire also makes a reliable binding material which does not corrode if the brush is stored for some time in water.
Brushes known as sash tools are bound with string which serves in place of a ferrule. This type gives satisfactory service, but has certain disadvantages which are as follows: (a) weakness of both binding material and cement; (b) the length of bristle necessitates further binding (known as bridling the brush) so that it may be more easily controlled.
Distemper brushes are assembled in a different manner from paint brushes, the former being con- / structed with a centre core of wood, to facilitate cleaning. When purchasing it is wise to reject any brush with a core of excessive thickness, I.e. more than one-third the total thickness; such brushes are inclined to open at the tip during use.
Before using a new distemper brush or one that has not been used for some weeks it is advisable to soak it in cold water for about twenty minutes. This causes the wood core to swell, tightens the binding, and thus helps to prevent any loosening of the bristles.
Storage of Brushes
Paint brushes in daily use may be kept in good condition by simply standing them upright in a vessel containing sufficient water to reach the metal ferrule. The average brush should not develop a twist unless it is placed at a slanting angle; a better method, however, is to suspend the brush in water or (in the case of a varnish brush) in a solvent oil.
Brushes not required for several weeks or more should be rinsed in paraffin or white spirit, to remove as much paint as possible, then washed with hot water and common soap (not soda) until no trace of paint remains in the roots (base) of the bristles; rinse well in clean water and allow to dry in a cool airy place. This treatment will also be advisable when a brush is to be used for pale tints following its use in a dark colour.
When clean and dry, brushes are stored in the same manner as for new ones, I.e. placed in boxes containing a little flake napthalene to prevent damage by moth larvae. Store in a cool, dry atmosphere, because heat causes undue shrinkage and possibly warping of the wood, and dampness induces mildew which may have a detrimental effect upon the cement.
Note: Varnish brushes, particularly, should be washed immediately after use, with soap and hot water, if they are not to be used again for some time. It is difficult enough to clean brushes in which paint has dried, but varnish incorporates a high content of gums, and when the varnish has once hardened it will not readily respond to the application of a solvent. Brushes used for cellulose paints should also be cleaned immediately by rinsing them in the correct solvent. They should then be thoroughly dried by rubbing them on a soft absorbent cloth.