One of the most important parts of kit building, or woodworking in general, is finishing. This is also where many of us can fall short. The attention you pay to sanding and finishing can make or break the quality of a piece of fine furniture. Here is a short review of proper sanding and finishing techniques.
The first three secrets to a good finish are sand, sand, and sand. If the surface you are going to apply a final finish to is not properly sanded it won’t make a difference how good the quality of the stain is - it won’t look good. So take your time, make sure you have good lighting, and use the proper grit for the proper wood.
First let me say that if you are not staining the wood, preferring to use just varnish or a clear oil based finish of some kind, you can go to as fine a grit sandpaper as you wish. The higher the grit, the smoother the final surface. If you are staining first, softer woods and more open grain woods such as mahogany need higher grit (Finer) sandpaper. We recommend going as high as 220 grit on mahogany. We also recommend using a good grain filler on open grain woods. If you are finishing cherry and are applying stain, don’t go above 150 grit sandpaper, except on the end grain. (More on this later.) The reasons for this are simple: gel stain will not adhere well and your wood will come out much lighter than you want. Also, woods like cherry tend to look blotchy when sanded too fine. Always use the lower grit sandpaper first and build up to the finer grits if necessary.
Break (slightly round over) any outside corners where two surfaces meet (unless it will be not be a part of a joint) with some sandpaper. This is important so that when doing any sanding or rubbing out between coats you do not remove the color or the finish on the corners. Finish tends to rub off much easier on corners than on flat surfaces.
- 120 grit - Use this for removing scratches or doing any rough sanding work.
- 150 grit - Use this for final cherry and tiger maple sanding. Use as an intermediate grit on mahogany or walnut. In other words: if you need to start with 120 for some rough work, remove the sanding scratches of the 120 with 150 before moving on to 180 and 220.
- 180 grit - Use this for open grain and softer woods, and for end grain on the harder closed grain woods. End grain will always stain darker than face or edge grain unless it is prepped first with higher grit sandpaper and/or a thin coat of varnish (See below).
- End grain - to sand end grain always go up at least one grit higher than you are using on the other surfaces. If you are sanding the face and edges to 150 grit, sand the end grain to 180 or even 220. To enhance this you may wish to put a very light coat of gel varnish on just before staining. You do not want the varnish to dry, so stain it immediately. Avoid getting the varnish on the other surfaces of the part or parts you are staining.
When you are ready to apply your finish, you should always wipe the entire surface with a tack cloth. Be sure to unfold the tack cloth first and crumple it up loosely to use. Open and re-crumple the tack cloth frequently to pick up more dust and avoid dragging foreign objects across the surface and scratching it.
Use two cloths to stain. One cloth is for wiping on the stain, while the other is for wiping off the excess. Use the same process for varnishing. Using a clean, lint free cloth, apply a liberal amount of stain to no more than a 2 square foot area at a time. This may be applied using a straight or circular motion. Using the second cloth, and working with the grain, wipe off excess stain and buff to a smooth even finish. Be sure to get any swirls or other marks out now so that they don’t dry. Wait at least 6 hours and apply a second coat of stain in the same manner. Usually, two coats of stain are enough to provide a nice rich color, but you may use as many coats as you wish. You may even want to combine colors, such as Brown Mahogany on your first coat, followed by a coat of Pennsylvania Cherry. (The top coat will be the dominant color.) Allow stain to dry 24 hours or more before applying the varnish.
Using a gel varnish is obviously nothing like using a liquid varnish, and the final result will largely depend on the method you use for application. The first thing to remember is that each coat needs to be very thin. The biggest mistake people tend to make with a gel varnish is leaving the coats too thick. You achieve the final look by the build-up of successive coats. At the same time, you do not want to wipe off all of the varnish when buffing out each coat.
Wipe on the varnish in the same manner used for the stain, making sure to cover the entire area you are working. Now, fold a clean cloth so that no loose corners of threads are hanging out, and lightly buff off the excess varnish in the direction of the grain. This step must be done carefully and will take some practice to perform correctly. This is especially true on larger, flat surfaces. The idea is not to leave any buildup but not to rub everything you have just applied off. Use light sweeping motions, getting progressively lighter until the cloth barely touches the surface. In this way you will rapidly buff off any excess varnish. Try to finish by going the entire length with each sweep so as not to leave break marks. Always check the adjacent edges for any varnish that may have run over and left a run. As you continue working on different surfaces, keep going back to previous surfaces to check for runs.
Lighting & Inspection
In order to leave the proper amount of varnish on the surface with each coat, you will need adequate lighting. As you finish each surface hold the work piece between you and the light at the best angle to reflect the light on the surface you are finishing. Turn the piece so that you can view it from all angles. There should be no raised or lumpy areas of varnish. The first coat of varnish will probably appear dull when you are finished. This, of course, will largely depend on how many coats of stain you first applied. As you lay on each successive coat, the shine will slowly begin to come out. After each coat dries, feel the surface to determine if you need to do a light sanding. Although Bartley Gel Varnish is almost dry to the touch immediately after application and actually repels dust, you may still have slight inconsistencies that need to be addressed before applying the next coat. Use a fine sandpaper such as 600 grit or higher, or use a #0000 or finer steel wool. Do not over-sand!
I recommend at least 4-6 coats of varnish, but you can continue adding coats until you are happy with the depth and durability.
Wait at least 2 weeks before waxing or polishing. This will give the finish time to cure completely. Polish with a soft, damp cloth and a good polishing compound, or you can use very fine steel wool and some wax. Buff out with another clean soft cloth.