The past two weeks I’ve been talking about sanding. I would like to continue that discussion with a look at more ideas that could be valuable to you in preparing your projects for their finish coats as well as sanding between coats once the finishing process begins.
Again, sanding is not negotiable. It’s a fact of life. It can be tedious. It can be dusty, messy, and a source of respiratory health issues. This is just the beginning of a whole laundry list of issues that surround sanding in general. So let’s build a bridge right here and get over all that. Let’s talk about things that are necessary to successfully applying finish to your projects.
White wood sanding (sanding the bare wood) is where we will start. My definition for thorough white wood sanding would be a consistent scratch pattern applied to the whole surface such that all high spots are removed. That scratch pattern is now obvious across all areas that were previously low spots in the surface.
Be advised that geographic location may tweak this next concept a bit. But consistently abrading the wood surface right before you apply a finish is essential at the South Pole as much as at the equator. It’s important on the sands of the Sahara as well as in the Everglades.
The key words here are right before. Why?
Because humidity affects that abraded surface. Wood “moves” due to moisture in the air. The amount of movement is dependent upon the amount of humidity in the air. The movement is subtle. Yet, the wood does swell and change. If you received doors last week from your door manufacturer and won’t be putting the stain on them until next week, you should think about how that time span will affect the surface of the wood. Why?
Let’s look ahead to next week. Let’s say you complete the cases, end panels, and trims next Thursday morning and plan to begin staining after lunch. The more freshly sanded parts may take stain differently than those doors and drawer fronts.
Also, are you familiar with your door supplier’s sanding schedule? Are you both prepping the same way? His white wood sanding schedule can make all the difference in the consistency of your stain job.
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Let’s move on. We here in the Northwest use a lot of alder. Known as “the great imitator,” alder can be very versatile. But one thing that it is not is blotch free. After you get past that, it’s a great wood. But for guys like me who have to match stain colors on alder, it’s a constantly changing canvas upon which to apply color. Someday soon we will go into how you reduce blotching. But for this discussion, consistent and thorough sanding is where you start.
I don’t often recommend this, but machine sanding with P220 grit is my preferred approach with alder. P220 closes the grain a bit more than what I usually like with other harder woods. But P220 also removes a certain amount of the surface in the process, and, assuming that you use good sharp paper, it doesn’t polish the surface. P220 shouldn’t leave too much in the way of swirl marks either. Remember, if you can still see swirl marks and you are going to apply a stain, then you’re not yet finished with white wood sanding.
Why do I mention the P220 thing? Because I try to stop my white wood sanding at P150 or P180. I want the wood surface open to receive the stain and not polished to the point of closure. That open surface, in turn, gives the seal coat something to hang onto. This becomes really important the harder the wood species involved. Adhesion of a seal coat to a finely polished maple surface, for example, is suspect. On clear coated maple, I stop at P120. The staining of maple is well beyond what we can talk about right here and right now.
Dull abrasives and a buildup of sanding dust on the paper are the enemies of good sanding. Tool Time Bernie (me) is a firm believer in concepts that will help you out here. We talked for a brief moment last week about Abranet abrasive by Mirka. Great stuff if you are using dust extraction…or not.
Dust extraction is the other thing. If you use sanders, do your respiratory system a service and figure out how to hook your sander up to some form of dust extraction. Other than the interference from the vacuum hose, there are more plusses than minuses to this. That goes double if you sand in the finishing room where dust is your enemy.
Tool Time Bernie is a Bosch tool guy. I love my Bosch sanders because I can hook them up to a vacuum hose and the dust goes where it should and not flying around the shop, up my nose, and down into my lungs. My shop is cleaner. The abrasive lasts longer, cuts better and generates less heat. My results are much more consistent. And, whether you use Abranet, Bosch, or something else, the holes in the pad and the paper allow the vacuum to pull the dust away. I use vacuum extraction on both my 5” random orbital and my ¼ sheet sander. We’ll talk more about dust extraction next week.
Two footnotes here; the orbit diameter and RPM of your sanders are the crucial numbers that determine sanding swirls. I use a random orbital with a larger orbit diameter for faster, more aggressive stock removal. I use my ¼ sheet sander for smaller, faster RPMs that will get rid of the swirl scratches.
Then too, when quality is at stake, I hand sand with the grain to finish up. I have a cool foam sanding block from Hermes Abrasive that uses Velcro-backed 5” sanding disks. Way cool and very ergonomic! Use foam pads and ScotchBrite on the detailed areas.
As for my approach to hand sanding, I went into my system approach last week. Please review that if you missed it. I try to finish sand by hand with P150 grit.
I always try to use good, sharp paper that lasts. I pay more for it but I get more from it. I like the red paper. Red Diamond is one brand. Norton is another. One of my friends uses Norton Champagne. That’s a mauve colored paper. All of these last longer, in my opinion and stay sharp longer. Sharpness requires that you develop some technique for the use of a “light hand” when doing your hand work.
Also, refer back to the previous two articles for information on scuff sanding between coats of finish. Scuff sanding is the second and equally important part of achieving a great looking finish.
Until next time…spray on!