Sanding a Tough Exterior
We posed a project scenario: you’ve got to sand an old splintery neglected exterior deck rail. How do you do it without getting wood in your hands or throwing down your abrasives in disgust? Festool and Blue Dolphin help “smooth” the way, and they both agree: life begins at 80!
Mike Bush, director of product marketing at Festool, wrote us a check by check, step by step.
So, your rail has not held up well in the weather, and paint is loose, uneven, and peeling off. First, evaluate the condition of the wood. Is it soft or “punky” (rotted), or is it dry and stable? If it is soft, you may need to repair connections, replace sections, or address any compromise in the structure before re-finishing. Painted surfaces can fail for many reasons, especially those exposed to the weather. We’re going to address solid, stable, and an otherwise healthy rail that just needs some TLC and a fresh coat of paint.
Let’s start by removing any flaking or peeling paint. This can usually be done fairly easily with a scraper or 5-in-1 tool. Don’t make too much of this—it shouldn’t be too laborious. We just want the easy-to-flake-off material gone so we can speed up the refinishing process that comes next with the sander. Once the loose pieces are chipped away, we can consider how to remove the rest of the paint and prepare the surface for new paint with a power sander.
Choosing a sander depends on the profile of the rail itself. Often, deck rails are not shaped like interior rails with their bulbous design, but instead are flat boards with softened edges that have been slightly rounded over to prevent splintering. Our task is broken down into two parts—first is paint removal, which we began with manual scraping and will follow up with power abrading. Second is to prepare the surface to a uniform and slightly smooth feel to provide a consistent and even surface for the paint to adhere. In the case of the smooth and flat rail board, we will use a dual-mode sander such as the Rotex from Festool. The Rotex have a mode that is gear-driven to provide aggressive and rapid stripping action to get us started. Once the stripping is accomplished, we can switch the sander over to a smoother random-orbital motion for final sanding.
One of the first things to consider regarding abrasives is how aggressively you want to abrade the surface. If you are unsure, always start with a higher grit than you think you need and evaluate from there. If the sanding seems too slow or is not aggressive enough (e.g. the paint is not coming off fast enough), move to a lower grit number. Although a coarser grit may strip a surface faster, it will also dig deeper and may leave scratch marks that must be dealt with later. Another consideration is the type of abrasive you use. Is it good for use on painted surfaces, or will it load and not cut? Festool has a line of abrasives for painters called Granat, specifically designed to avoid the loading all too common when sanding paint and other finishes.
Once the surface is free of the old paint we can address bringing the surface to a smoother, more attractive feel. If you started with 80 grit for the removal process and used the gear mode of the sander, the next step is to stay with the 80 and switch the tool to the “random-orbit” mode. This mode has a different stroke pattern and will help to “erase” the pattern left from the aggressive gear-driven mode that was used to strip the surface. By using the 80 grit we stripped with, we are still abrading to the same depth, only with a different, less aggressive, pattern.
Now for some grit progression, as the surface has been stripped and we want to smooth it out further. It is a good ‘rule of thumb’ to follow a numeric sequence of grits to ensure the best finish. Skipping abrasive grits may lead to a less-than-smooth surface or leave behind tell-tale swirl marks (also called pigtails). For our example, if I started with 80 grit to remove the old paint and start the surface prep, I may move to 100 or 120 grit. I would not jump more than one grit number as each grit’s job is to erase the “scratch” marks of the one before it.
Using a normal random orbit sander can generate a fair amount of dust. A gear-driven sander like the Festool Rotex can generate even more dust in the same amount of time due to the highly-efficient removal rate. In order to best contain this dust and prolong the life of the abrasive, it is best to use a dedicated dust extractor.
Festool provides dust extractors that allow you to plug the sander directly in at the extractor. This allows not only a convenient power option, but also serves as a tool-triggered operation. That is, when you turn on the sander the extractor turns on automatically. Likewise it turns off automatically when the sander is switched off. This provides dust extraction when you need it for a cleaner surface, longer lasting abrasive, and cleaner air.
Festool designs sanders, abrasives, and dust control measures that help prepare surfaces faster and with better results. Word of caution though—using Festool for your surface prep may lead to more jobs and extreme customer satisfaction!
Roland Kolilias, president of Blue Dolphin Sundries, introduces a new 5″ disc.
If your wood has endured, for example, five years of weathering and peeling due to poor prep on the last redo, you have several steps to follow for your own redo. With the old coat failing and the wood being exposed to the elements for those five years, you will have peeling paint, mold, and raised wood grain.
Step 1: Lightly power wash to remove all loose coatings.
Step 2: Remove all the loose paint and splinters using a sanding technique. I would recommend a random orbital sander to have the job get finished in the correct way. Now, you can use it with the new Barracuda 5″ multi-hole discs from Blue Dolphin Abrasives. These are manufactured with premium white aluminum oxide, treated to resist loading. The multi-hole design allows the discs to stay cooler, so they last longer.
They are also designed to fit any make of random sander on the market, so you have less abrasives to carry in your toolbox.
Step 3: Start with the 80 grit to finish removing the old paint and smooth down the raised grain and splinters. After the 80, start moving up in grit to reach the desired smoothness recommended by the paint coating manufacturer.