Staining and Finishing Wood-Carvings – Hints and Tips by Richard Colbran//
1. Staining
Most convenient to use Wood-Dyes (Rustins, Colron, Liberon). These are stains available in a range of shades which can be blended or thinned with white spirit.
- Apply first, to raw, prepared wood, as they will not penetrate a sealing coat. Remember that end-grain takes stain much more readily, so use diluted stain or pre-treat end-grain areas with thinned sealer to reduce absorption of dye.
- If polyurethane varnish or oil is to follow, leave ample time (several days in a warm place) for stain to dry out. Otherwise carving will remain sticky.
- When staining a carving, areas which need to be left unstained can be blocked first with cellulose sanding sealer (dries very quickly), and any stain in the wrong place can then be wiped off with rag dampened in white spirit. Alternatively, stain which has bled into the wrong area can be carefully chiselled away, to expose unstained wood.
- Sometimes, a deep knife cut along a stain boundary will stop the stain bleeding across.
2. Applying the Finish
Sanding Sealer (SS) is a useful tool in the carver’s armoury.
Sanding Sealer is intended for use as a foundation coat before further polish is applied, and consists of a sealant mixed with a small amount of filler material. The sealant base can be cellulose lacquer, shellac (French Polish), polyurethane or acrylic so it is important to use the correct solvent if the product needs to be thinned. Solvents can be cellulose thinners, methylated spirit, white spirit or water. So read what it says on the tin!
If the grain is raised after application, a light rub down may be necessary.
As mentioned, it can be used as a stain-resist where differential staining is required.
- Where carving problems arise with short-grain or soft patches, the application of one or more coats of SS, thinned down with appropriate solvent, to increase penetration, will harden up the wood, making it much easier to carve (Superglue can also be used for this purpose). Always bear in mind, however, that wood treated in this way will not subsequently take stain like untreated wood!
- A primer coat of thinned SS (+ 10% thinners) is a good start before waxing or PU varnish application, and will speed up the drying of the first coat of PU, especially on stained wood.
Polyurethane clear varnish is a good, durable finish, but should be thinned down (+ 10% white spirit) to avoid a treacly appearance. Satin and matt versions are available, and are often more suitable for carved work.
- For exterior work, select a varnish with UV inhibitor and flexible build, to minimise cracking ( eg. Rustin’s Flexterior varnish),
Oil finishes are easy to apply – wipe on, wipe off at increasing intervals, and give an attractive appearance.
- They often enhance the grain of the wood, so make sure that this will be acceptable in the finished carving.
Acrylic varnishes are increasingly popular for Health and Safety reasons, and there are some good weather-resistant types available which are suitable for out-door carvings. They dry quickly and can give a nice satin finish.
Acrylic paints can be used, then over-varnished to give improved weather-resistance.
French Polish is more suitable for furniture than carved work but can be used as a base for subsequent wax polishing.
Wherever possible, do a trial finish on similar wood before risking your precious carving!
R Colbran 17/12/2012
A useful reference book:
Understanding Wood Finishing – How to Select and Apply the Right Finish
Bob Flexnor
Hardback – Fox Chapel Publishing, Paperback – Readers Digest