Preparation of wood surfaces before oiling
Whatever woodworking is planned to be carried out, the first work process will be the proper preparation of the wood surface. One of the most important steps in this is sanding. Fortunately, everyone can polish it - but it doesn't matter how. You can choose from very different solutions depending on the purpose, the wood surface and the workflow you are preparing for. We have gathered the most important factors that are definitely worth considering so that you can find and achieve the right method and end result for you.
Why do I want to polish?
Basically, sanding is used in three cases: 1. to form precise parts (eg to achieve optimal joints), 2. to roughen the surface before gluing, and 3. to remove residues from previous surface treatment to prepare the surface treatment. So that you can do the sanding with the right tools and in the right way, the first step is to determine the purpose of the sanding. We are now choosing Objective 3, so you can read more about sanding in preparation for surface treatment in the future, and learn more about the other two paths in our blog posts.
How big and what wood surface will I work with?
Depending on the size and design of the wood surface you want to prepare, you can choose between two sanding techniques: manual or machine sanding. By definition, in the case of smaller, more articulated workpieces (eg a finished piece of furniture that we want to renovate), it is worthwhile to grind by hand, while if you can work with furniture boards or cut-to-size wood, you can choose machine grinding. You can sand by hand with sandpaper, an abrasive pad, sandpaper or even an abrasive sponge. Today we also have many options in the field of small machine grinding, most often we use eccentric and vibratory and belt grinders. Of course, there are also larger disc sanders for floor sanding, which we will not cover now.
What kind of abrasive will I need?
The right choice of abrasive is the key to all abrasions, as well as to the preparation of the wood surface treatment. This is one of the factors that has the greatest impact on what surface we get in the end, what our woodwork will look like by the end of the surface treatment. For this reason, it is very important to be aware of the most important property of abrasives, abrasive grains. Abrasives always show the fineness of the grit, this numerical value can be found after the “P” mark, e.g. P60 or P120. The numerical value actually indicates the number of equal grid openings per inch on the substrate. The finer the grains (i.e. the smaller the grid opening), the higher the number - the finer the sanding:
P12 - 80: coarse grinding; to eliminate surface defects and unevenness
P100-120: intermediate grinding; removes scratches and marks on rough sanding
P150-1200: fine grinding; final smoothing, greatly affects the final quality
In order to achieve the desired result, it is necessary to use abrasives of different finenesses, and they are always applied in the correct order. If a grit is left out, our sanding will eventually be uneven, leaving sanding marks on the wood surface to which the color pigments adhere and, depending on the color of the wood oil chosen, slightly or severely deteriorating the appearance of the finished wood oiled surface.
What is the grinding process? What is the correct grain order?
For wood surfaces to be treated with wood oil, it is even more important to follow the correct grain order than for varnished or painted wood surfaces, as the adhesion of wood oil is also affected by too fine sanding, not only coarse (see later).
The order of the grains and the number of sanding cycles depend on the size and number of overhangs between the individual wood elements, but also on the degree of soiling and the unevenness of the wood surface.
Adherence to the grades actually means that with the next grade you should always be able to remove traces of the previous grade of sanding, while keeping from coarser sanding to finer sanding. So if you start grinding with a grain size of P60, the next grade should be P100, not P150 at all. Do not jump too much between the steps so that we can nicely remove the traces of the previous sanding. The following figure illustrates the grain sequences:
Source: Tudástár – PEZA Kft.
When preparing a wood surface to be treated with wood oil, it is advisable to sand the surface thoroughly, without scratches, up to a grain size of 120.
Tips and good advice for sanding
If you choose our Rubio Monocoat Oil Plus 2C indoor wood oil to treat your wood surfaces, we can also provide some special suggestions to make the end result really right for you:
In the case of colored wood oils, the color pigments need an adhesive surface, so if the wood surface is very highly polished, it may be more difficult to color it. The ideal particle size is therefore 120, at which time we allow the wood oil to adhere to the wood for about 10 minutes. For surfaces with a higher polish, it takes more time for the wood oil or color pigments to form suitable bonds, so allow to act for about 20 minutes before wiping off any excess wood oil. The waiting time, of course, depends on the conditions of the wood surface treatment (humidity, temperature).
If you want to achieve the most intense staining with a coat of wood oil, we recommend that you also use our Rubio Monocoat Woodprep surface preparation product before applying the wood oil. It is very easy to use: it is applied to the surface richly with a brush, but without puddles, and then, if the wood is dry again, it is ready for oiling.
If you want a completely black wood surface, you can do it with our RMC PrecolorEasy - Intense Black wood stain and our RMC Oil Plus 2C - Black wood oil.
Finally, here are some general good tips to keep in mind for any grinding job:
It is especially important to sand in the direction of the fibers whenever possible and to avoid cross-sanding. If sanded crosswise, the wood fibers can be damaged, ie they will open, the wood surface will be rougher in these places, at the same time it will absorb more color pigments, so the wood surface will be darker here - the end result will be uneven, stained.
Wear a dust mask and always sand in a well-ventilated room, so try to get as little dust as possible into your body during sanding. Inhaled abrasive dust, especially oak, is especially harmful to our health and harms our lungs.
Fix either the material to be sanded or the sanding tool, depending on their size and mobility. For proper and safe sanding, it is essential that one of the segments is well secured and that we can exert the right force without unexpectedly moving our piece.
When working with an eccentric sander, make sure that the eccentric sander is intact. This is because if the sanding sheet is damaged, it sands circular scratches on the wood surface. These circular sanding marks will also be visible in the end result, so we will have to do the sanding again to get a beautiful, scratch- and stain-free, even result.
Always keep the work surface clean. As with any work process, it is important to have a good idea of what you are doing when sanding - this requires you to remove accumulated chips and dust from the surface from time to time. It helps a lot to check our sanding with a lamp, illuminating the surface with shadows so we can see where more treatment is needed.
If you have any questions about sanding, surface treatment, or our wood oils and wood preservatives, please leave a comment or write a message to the email address shop@rubioshop.hu and we will be happy to help.