Wood Finishing Tips – Abrasives And Adhesives

A clear finish may sometimes disguise or obscure the grain, but it will never cover imperfections in the surface of the wood. Rather, it will emphasize them. The more work you put into sanding, the better your chances of a first-class finish.

Abrasives
Abrasive papers are made from glass (flint), flour, garnet, aluminium oxide or silicon carbide. Glasspaper is the cheapest, but it also wears out quickest. It has no real advantages over garnet, which gives a more ‘sympathetic’ cut, and hardwoods seem to like it better. Aluminium oxide papers are expensive, long-lasting, and are usually used with machines. Silicon carbides (wet and dry), though available in coarse grades, tend to be used for cutting back between coats, especially of hard synthetic lacquers. Lubricate them with water, white spirit (paint thinner) or mineral oil. Avoid using liquid paraffin or mineral oil, which are insoluble in meths (wood alcohol), on raw wood. Raw linseed oil is usually better.

There are at least three marking systems, of which the easiest one is the ‘ordinary’ numbers, starting at 30 or 40 for the coarsest grades. A 30/40 grit size is the same as S2 for the glass and 1-1/2 for the garnet; 100 grit is F2, 2/0 garnet; and 150 is 1 glass, 4/0 garnet.

Steel wool is used for stripping in nooks and crannies where no tool blade will go, for surface repairs and reviving, for cutting back between coats, and for final burnishing, usually with wax or oil. The coarsest grade available is 3, the very finest is 0000 or 4/0.

Pumice and rottenstone are fine powders – pumice is the coarser – usually mixed with oil to make an abrasive burnishing paste. The friction they create is also an effective remover of blemishes in shellac finishes.

Car polishes, including T-Cut, can be used. Any really fine abrasive paste, even toothpaste, is good in the last burnishing stages.

Adhesives
Animal (scotch) glue was about the only furniture adhesive there was until the 1950s, and you are bound to come across it in repairs. It is used hot, and can be melted – with care – with hot water or an iron to make it stick again.

PVA (yellow) is the most commonly used adhesive nowadays. While not waterproof, it is extremely strong. Time and pressure are needed for it to set effectively.

Formaldehydes are usually bought in powder form and mixed with water for application. They are harder to use than PVA, but are waterproof.
Impacts (contacts) are good for sheet materials but unforgiving because they stick immediately, unless you use a ‘thixotropic’, which allows some re-positioning.

Two-pack epoxies set rock-hard. They are useful for filling and building up in woodwork.


Tauqeer Ul Hassan
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