Water-based finishes

The quality of water-based finishes, or water bases, has improved over the years; you can now find quite unproblematic products on the market although they are often still quite difficult to work with. Waterbases are tiny droplets of finish emulsified in water which interlock while curing. Don't be fooled by the cloudy, milky color of the finish inside the can, and don't draw any conclusions from this about the eventual color.When applying two coats of water-based finish on top of each other, the one applied earlier has to be allowed to fully cure first to prevent water from remaining in the lower of the two coats. Water-based finishes cure only slowly and the surface remains soft and gummy for some time before fully hardening. Down-sides of water-based finishes are their extreme sensitivity to high humidity during their application or the fact that they are less easy to polish: because the individual coats dry one after the other, patches can develop if one coat is rubbed off partially. Water-based finishes do not change the color of the wood. They need a very smooth surface because they bridge pores and scratches and thus create air pockets that refract light at various angles, making scratches more visible.

Using a brush

A well-applied brushed finish is arguably better than a badlyapplied sprayed one. Unless you use cans, spraying a guitar always requires a lot of preparation, a suitable room and expensive equipment. You should really seriously ask yourself if a brushed finish wouldn't also meet your own personal demands, especially because they require far less in the way of preparation and are also much cheaper. For only a small part of the money you would otherwise have to spend on spraying equipment you can already buy the best brushes available on the market. Always use soft, good-quality brushes and remove any loose bristles before you start painting by hitting the brush against the edge of the workbench or against your palm. Then dip the brush in lacquer thinner, wipe it off and clean it with a clean cloth. If you prepare the brush in this way, the finish will flow better and also the cleaning afterwards will be easier.

Brushed finishes can be of a very high quality if a few things are heeded. Only dip about one third of the brush into the finish and then squeeze the bristles gently against the edge of the container, taking care not to wipe off the brush to prevent air from getting into the finish via the brush, which would lead to bubbles forming on the surface. Hold the brush at a maximum angle of 45 degrees to the surface and spread the finish with long, even strokes, making sure that the material flows slowly and gently from the bristles onto the surface. Between their bristles all brushes have a small cavity from which the material can flow. Only the front third of the brush ought to be in contact with the wood. Practise on scrap wood first to find out whether the material flows well; add a thinner if necessary. When applying the finish to the body start brushing at some distance from the edges and brush towards them to ensure that any excess material doesn't run down the sides of the body. Then place the brush back at the point where you started and paint towards the opposite edge. When you reach the edge slowly raise the brush, as if imitating a plane taking off. Finally, brush the finish onto the sides. Don't move the brush too quickly - good results will only be achieved if you take your time and do the brushing-on slowly. Also, never brush over a coat that is still wet. When the first coat feels dry, brush on a second and then wait for one to two hours before finish-sanding the surface with 400-grit wet/ dry paper and a bit of water. After that apply another coat before sanding it again as above. Repeat this process as often as necessary until the surface is smooth and free from blemishes, but avoid applying too many coats. Flat, satin and semi-gloss finishes are the ones easiest to apply; gloss finishes require more careful work and attention.

Water-based finishes are best brushed on with a special brush with flagged bristle ends.

Keeping brushes in good shape contributes significantly to good finishing results. Often cheap brushes are bought because one assumes that it won't be possible to clean a brush sufficiently well after use anyway. This is, however, a totally wrong assumption. The following instructions for cleaning are intended to give you long-lasting delight with more expensive, good-quality brushes; always carry out all steps of the cleaning process whenever a brush has been used and don't just leave a brush soaked in a solvent-filled container overnight, not even if you intend to continue painting the next day already. Follow these instructions and you will be rewarded with brushes that remain in perfect shape. First remove any material left on the brush by squeezing it against the walls of the container. Then wash the bristles in a sufficient amount of thinner and, wearing protective gloves, massage them thoroughly with your hands. After this twirl the brush between the palms of your hands so that any solvent left is removed. Don't worry about using too much solvent for washing the brush: it won't go off and you can use it again later. If you leave it to stand until the solid particles have settled to the bottom of the container, you can pour it through a coffee filter and get fairly clean solvent again for the next time you need some. After the brush has been thus rough-cleaned, wash it properly in a mixture of plenty of warm water and a bit of hair shampoo by running your fingers through the bristles (commercials will tell you what shampoo to use!). Then wash out the solvent with running water. Repeat and rinse the bristles a second and a third time with fresh water. Finally, carefully wrap the bristles in paper and put a rubber band or adhesive tape around it to hold the paper in place. This will ensure that the bristles remain straight while the brush is not used.

Conversion finishes

Conversion finishes are particularly hard and durable and fast-drying; only two coats are usually needed. They harden in a chemical reaction and individual layers do not dissolve each other. Like water-based finishes they are therefore less easy to rub. Before applying a conversion finish it often has to be mixed with a catalyst (for details always refer to instructions on the can). Only prepare as much of the mixture as you will be able to use within eight hours. Conversion finishes have a few disadvantages as well: their fumes are toxic, their shelf life is limited (once a can is opened it has to be used within 12 months) and they are not cheap.

Using foam rollers

Using foam rollers also gives good results. They are cheap and produce an even finish. Pour some well- stirred-up finish material into a small tub (available from paint stores). Spread the finish thinly and evenly on the roller by rolling it in the tub, wipe off the excess at the edge of the tub and apply the finish all over the wood, moving the roller evenly. I only use such rollers once and don't even try to clean them with solvents; all solvents have to be somehow disposed of as well (in practice they are, sadly, often poured down the drain and end up in the sewers), and even with large amounts of them the rollers could not be cleaned properly anyway. I think that my approach does less damage to the environment. If you put a used roller into a plastic bag and squeeze out the air to make the roller stay soft, you will be able to use it for another coat so that not more than two rollers will be needed in most cases.