Wood Surface Preparation Guide
Step 1 in preparing wood for paint or stain – Fill in any deformities
Before you begin considering sanding the surface down, review your wood project to ensure there are no holes or gaps in the wood surface that you want to address prior to getting your wood project ready for paint or stain. If you do have holes or gaps in the surface there are three options available to fill in trouble areas in your wood surface. For small problem areas options like scratches and dents that are little you can use wood putty, shellac sticks, or wax sticks. Wood putty tends to be one of the easiest as you simply lay the putty in the defect smooth and then after it has been applied you can sand the putty. Putty color can be changed after it has been smoothed. Shellac sticks are melted and drip into the deformity making them a little more challenging to work with but are still a great option. Finally, you have wax sticks which require the wood to be sealed so if your wood is finished a wax stick can be applied directly but if your working with the wood prior to being finished you have to seal the wood before using the wax stick. Wax sticks are typically offered in a variety of colors making them well suited for color matching if your wood is already finished and your looking to fix a small deformity.
Large deformities will require a cut out from another piece of wood that is then inserted into the boards large hole. These are typically called a Dutchman and this article covers how to make a Dutchman.
Step 2 in Preparing Wood for Paint or Stain – Smooth the Wood
After you have fixed any surface defects whether they are small or large, next it is time to get the surface properly sanded to receive the coating you will apply, whether it is paint or stain. To properly prepare the surface, it is important to review the types of sandpaper you can use and why you may consider each type as well as the types of sanders available.
Sandpaper Types – Most Popular for Wood Working are in Bold
- Glass – glass paper is one of the cheapest forms of sandpaper available. It usually breaks down to easily and is not a great choice for wood working.
- Garnet is made of a mineral and has a reddish tint to it – It can be a good option for cost effectiveness especially with soft woods
- Aluminum Oxide Sandpaper – Aluminum Oxide Sandpaper is very durable and is a great option to use with wood projects
- Silicon Carbide – Generally silicon carbide sandpaper is black in appearance. It is the most durable of sandpapers but can tend to be to aggressive for use on prepping wood
Sander Types –
- Orbital Sander – An orbital sanders pattern is circular and can be a good sander to prepare the wood. Orbital Sanders can sometimes leave circular scratches in your wood surface which can show up when you go to stain your wood.
- Random Orbital Sander – A random orbital sander is also smaller like an orbital sander but the pattern which sanding occurs is random, this reduces the likelihood of leaving behind any marks that may occur with an orbital sander. A random orbital sander is one of the most popular options for preparing wood to be finished.
- Belt Sander – A belt sander can remove a lot of material in a short amount of time. However, if you fail to use the belt sander properly it can also damage the final appearance of your wood surface.
Once you have figured out the right sandpaper and sander, next comes the process of sanding the part. You want to start at a lower grit and gradually move to finer grit sandpaper. Start with a 60 or 80 grit sandpaper and you can stop sanding at around 150 or 180 grit. At 220 grit or above the wood actually begins to become polished, which means it will block absorption of stain. If you will be using a penetrating finish like tung oil 220 grit is ok.
Raising the Grain
If you will be using a water based stain, after you have sanded your wood to 150 or 180 grit, you will want to wet the wood with water and allow the water to dry overnight. The next day you will reuse a fine grit paper (150 or 180 grit) and knock down any grain that stood up due to the water. Raising the grain ensures your wood will stay smooth after applying initial coats of stain and sealer.
Step 3 in Preparing Wood for paint or stain – Remove any surface contaminants
Once you have properly sanded the wood, the final step is to ensure any contaminants like glue and dust are off the surface prior to beginning to stain or paint the wood. To remove glue you can use acetone for the majority of wood glues. For sawdust and similar contaminant make sure you use a tack cloth, blow down the surface, or use a vacuum to clear any dust that is created off of the wood’s surface.
Step 4 – Apply Stain or Primer
If you will be staining the wood after you have properly prepared the wood surface you should then apply a stain or if you will be painting the wood then apply a primer. After applying primer you will sand the primed wood surface before applying your paint to the wood. The stain you will apply and then apply a topcoat sanding after the initial topcoat and in between every layer of topcoat but the last.
Tips for repairing just the top coat of wood
If you are only wanting to repair the top layer of finish (the shiny layer) you may be able to simply briefly sand the top layer and apply new top coat or you can use a deglosser to remove the top layer and apply a completely new topcoat.
Tips for repainting or restaining wood
If you will want to completely change the color or stain on your wood you will have the best results sanding the wood so that the coating is completely gone and if painting applying a primer or if staining beginning to apply your new stain. A quicker option if you plan to paint the wood is to remove the topcoat and use a primer prior to repainting.
Tips for repainting large Wood Surfaces
If you are repainting a log home or similar structure you will want to sandblast the surface to remove the original coating. After sandblasting you will want to sand the surface common blast medias used for removing the coating from log homes include walnut shells or corn cob.