Sanding is the process of smoothly polishing a surface especially wood with a mechanical sander or sanding paper. Sanding paper are often the most common choice of use for many who want to sand a surface.
You must have heard of sanding paper right? They are the unconventional papers that makes your wood smoother or rougher depending on what you want.
A better finish for wood work is achieved when both the first and second coats of stain bind together perfectly and sanding takes away the edge of roughness off(literally) which allows for that to happen.
Sanding between coats of stain has always been a controversial topic in the engineering and woodwork space so you are probably looking for answers to the bugging question of whether you should sand between each or not.
The Need for Sanding between Coats of Stain can Depend on
Sanding can also be dependent on the time that the coat of a stain is allowed to dry. Most coats of stain that are sanded by wood workers is usually the water based stain or the water soluble dye stain. For this reason, it is important that the water is allowed to dry for a little bit which takes about three to eight hours depending on the humidity level of the occasion. Once a surface is deemed dry enough by touching, it can be sanded before another coat of stain is applied.
The Type of Wood Stain
Oil Based Stain: When people think of staining wood, the foremost idea of stain to use is often the oil-based stain as it is the most popular and easiest to use. For an oil-based coat of stain you need not sand between the coats because of its longer window of drying time.
Oil based stains with its longer window also gives enough time to easily wipe the extra stain off with a rag cloth before applying a new coat of stain.
Sanding can however be beneficial for an oil based stain if it is done at the preparation stage to smoothen out the surface and get rid of debris before applying stain. If you are trying to achieve a dark stain, you can sand lightly between each coat with the finest of sandpapers usually from 400 grit and lighter.
Water Based Stain: However for a water based stain, it is compulsory to sand because water does not allow for a smooth finish and surface, sanding helps down all wood grains to make for a perfect finish. For a water based stain, each layer of a coat is required to be sanded to reduce the bubbles on the surface.
Gel Stain: Just like oil based stain, wiping excess stain off with a rag will do just fine but you sand lightly at the preparation stage.
Lacquer Stain: It has the characteristic of melting down below each other while painting over coat so it smoothens out easily without any sanding between each coat. Of you however still see defect between each stain, you can sand very lightly to keep the surface spotless before another coating.
Polyurethane or Varnish Wood Stain: This type of stain can either be oil based or water based and surprisingly for both types, sanding is absolutely unnecessary. The chemical component in both types allows it to dry very quickly without affecting it’s surface. If you do decide to smoothen further by sanding, it might make the surface uneven which is not advisable.
Metal Complex Dye Stain: This type of wood stain is fairly uncommon and fits perfect for denser or heavier wood and outdoor furniture. The metals added to this type of dye do not raise wood grains so no sanding is need at all between each coat.
Water Soluble Dye Stain: For a water-soluble dye satin, it comes in a powder form which has to be mixed with water so it does need a light sanding in between the coats of stain for a smooth finish without bubbles.
To sand water based type of stain, you should start with an 80 grit and paper to lighter types.
If you feel unsatisfied with your coating and what to sand, by all means do so but should use a very light sand paper e.g. 400 grit sandpaper.
How to Sand between the Coats of Stain
To begin with, select a high grit(about 240 grit) fine sandpaper depending on your type of stain.
A high grit sandpaper smoothens out slowly while a lower grit can easily scratch your work surface. Never use steel wool to sand between your coats of stain except you are working with a large surface area.
Pick a sanding tool that would be convenient for you to work with, you can as well hold the sanding paper in your hands.
Next, while sanding, ensure it is done in the direction of the wood grain with light passes across end to end. When you notice white dust settling, run your fingers across the surface to check if you are satisfied with its smoothness, you can always continue until it is perfect for you.
Vacuum all the dust off and clean further with a dry cloth. Never use a wet cloth to clean to prevent raising further wood grain. However, if you are using an oil based stain coating, you can wipe the surface with a cloth soaked in mineral spirits to get all the dust away.
In conclusion, Yes it is very necessary to coat between your stain but it is not necessary for all kinds of wood stain. For any water based stain, if you sand between coats of stain, you are on the right track and it is very necessary.
However, if it is any other type of wood stain, sanding is optional and if you are a perfectionist you can smoothen the surface a little bit more but you must stick to the lightest sand papers possibly from 400 grits and lighter. You should also sand very carefully and with patience, slightly dusting after each sand from end to end to see if it is perfect enough. This is because it can make the surface uneven and prone to tears and scratches difficult to remove, thereby ruining all the work put in.