How to Prepare Wood for Refinishing
The first thing you will need to do is decide what you want your piece to look like in the end. Do you want a stained piece or do you want to do a paint technique? This will make a difference on how to prepare your wood. It also matters what condition your wood piece is in before you start in how you will finish it. There are many things to consider before you start. Some of which is your piece currently stained or is it painted? Do you want to paint your piece or re-stain it? If your piece is painted and you want to repaint it you may be able to just paint over the old paint. But that is only if the old paint is in good condition and without peeling, chipping and cracking. Now if you want to do a paint technique such as crackle or craze you can put the crackle medium right over the old paint (provided you like the color) and then apply your finish coat.
You also need to know if your piece is made of real wood or if the finish is a veneer. If it is a veneer finish you will want to take extra precautions especially if you are going to be sanding it. It can be sanded but keep in mind that veneer is very thin. A veneer is not going to tolerate as much sanding as a solid wood piece.
Using a stripper or paint thinner
This process can be really messy, though I find it therapeutic. If you have never used a stripper it really isn’t hard. It is a matter of applying the product and waiting. The waiting is the hardest part. Follow the manufacturer’s instructions on the back of the can. Make sure you are in a well-ventilated area and that you have paper or something under your piece. This process is very messy as I stated before. You should also where gloves and protective glasses.
The type of stripper you buy can make the job easier as well. If you have a piece that you can lay flat a liquid stripper will work just fine. I prefer to use a gel stripper on my pieces. Gel tends to grab ahold of the piece and doesn’t run. I also feel like I don’t have to reapply as much as I do with a liquid. Remember when applying to apply a generous coat and don’t go back over it. Once it has touched the wood it has already started the stripping process. So if you manipulate it you will slow down and possibly stop the process.
Typically you will have to strip a piece at least twice before you have all of the paint off. Possibly more depending on how many coats of paint the piece had on it and what type of finish it had as well. Varnish can be tough to get through.
When it is time, scrap as much of the paint as you can taking care not to gouge the wood. When you get to the point where there is just a thin film of paint left soak steel wool in the striper to remove the rest. You can also at this point use paint thinner using care to make sure you have proper ventilation. If the paint is embedded in the wood you can at this point use a soft bristle wire brush. This will help get the rest of the paint from your piece.
Some strippers require that you remove residue with lacquer thinner or mineral spirits. Others use water. Check the manufacturer’s directions and follow them. After removing the residue let your piece dry for at least 24 hours.
Now that your piece is free of its old finish now it is time for the next step.
Using sand paper to prepare for a new finish
What is sand paper? Sand paper is made up of tiny particles on paper. The particles on sandpaper are made up from a number of sharp edges that cut the wood. The grit is a reference to the number of abrasive particles per inch of sandpaper. The lower the grit the rougher the sandpaper and conversely, the higher the grit number the smoother the sandpaper. The grit you use depends on what you are trying to do.
By going through the grits, starting with the roughest (or lower number sand paper) and working with each progressive piece of sandpaper will remove the scratches from the previous piece. Skipping grits to save time is not necessarily a good idea. By skipping grades of sand paper it can lead to sanding longer just to remove the scratches left by the previous grit. Following the grits is more important with harder woods like maple than it is with softer woods like pine.
What grit is best?
If you are planning to use a water-based stain it’s best to sand up to a 200-grit sandpaper. Medium and fine grades of sandpaper are generally used in refinishing furniture and antiques. Coarse grits (those under #100) can damage a fine wood finish. Medium grits, such as #120 and #150, are useful for removing old finish or scratches. Fine grits, such as #220, are frequently used for a final light sanding just before applying stain to the wood.
Grades of sand paper
There are two different grades of sandpaper on the market commercial and industrial. Commercial grade is commonly available to the public at hardware and home improvement centers. The industrial grade is usually available only through industrial supply stores. It’s made from higher quality materials and is designed to be used in production lines.
The use of power tools
Power tools make sanding go faster. There are several options of power tools you can choose from but heavy-duty ones such as belt sanders are designed for heavier carpentry work and could quickly ruin a fine antique. A palm sander, a lightweight rotary sander, is more suitable for refinishing.
How to sand
You will want to always sand in the direction of the grain--never perpendicular to it or at an angle. If you don’t stick with the wood grain you will make scratches in the wood that will show up when your piece is stained. This also applies when working on edges and hard-to-reach corners. Scratches made by sanding against the grain will look unattractive on the finished piece and will be particularly noticeable after staining.
Some of the wood dust from sanding will become airborne, so you need to wear a particle mask while working. I typically start with 120 grit and finish with 220. This should give you a nice smooth finish. The care you take when sanding will show in your end results when staining, varnishing or using polyurethane.