Learning to Like Finishing, It May be Possible!
This might be my shortest opening message and I have a very good reason for this as you will see.
This month we welcome back Scott Burt and his words of wisdom on spray finishing.
I must admit that I enjoy reading the articles he writes for our newsletter and frequently he mirrors many of my thoughts although often more elegantly stated.
Instead of reading a long message from me, I suggest that you read his feature article this month more than once. You will find, as did I, that each time you read it through more information comes to you. Scott’s thoughts reinforce the need to not only connect with your spray application equipment but also the coatings you plan to apply and all aspects of the finishing process. It is a pleasure to read his article because he gives wonderful advice, and his writing is unique!
I would love to hear back from you after you have read Scott’s article.
Sr. Vice President, Sales & Marketing
Apollo Sprayers International, Inc.
Finishing Feature Article by Scott Burt: The Twist of Variables
"While we use machines in finishing, we are humans who have to understand how to think like a machine, without being consumed by it."
Regardless of whether you are a serious professional finisher or a home woodshop nut, if finishing is part of your program, you have a lot going on in your craft.
There is a lot to finishing. We all try to keep it simple, but that is a trick that we have to pull on ourselves. Finishing is easy. Finishing is easy.
Finishing is not always easy
First off, we all talk about doing it the same way every time. Creating finishes is like watching snowflakes fall. No two are identical. Even if two pieces are identical and being finished simultaneously in the spray zone, they are never identical because they are happening at two different spaces in time, with a twist of variables.
You can rarely replicate anything exactly. Finishing is too subjective, and the better you get at it, the more your eye becomes brutally honest with you. READ MORE
Product of the Month: Erecta-Rack Drying Systems
Once you've seen and tried Erecta-Rack, you'll be so glad you bought it. The Erecta-Rack is a simple, patented, innovative solution for all of your trim and door drying needs. It is completely modular and portable. You just insert the cross bars into the support blocks and you are ready to go! When finished, simply disassemble and transport in the custom carry bag. Available in sets of 5 or 10, you'll be saving space, time and working more efficiently. Whether you are in a space restricted workshop or at the work site, you'll be able to dry more, faster than you ever thought possible.
Finishing Tip by Bob Flexner: Staining Sapwood with Dye
The easiest way to stain lighter-colored sapwood so it blends with the heartwood is to stain all the wood with a dye stain, as is shown on the right side of the accompanying picture of walnut. Dye is much more effective than pigment, or any commercial stain that contains a binder.
You can apply the dye several times after each application has dried to get a darker color. Or, with water-soluble powder dyes, such as those from W.D. Lockwood, you can wipe over the stain with a water-damp cloth to remove some of the dye and lighten the color.
You can also apply more of the dye just to the sapwood, after you have stained all the wood, to selectively darken it and achieve a closer blend. But applying dye just to sapwood, and not to all the wood, seldom works well because it’s so hard to get a match – though you could always try it. The worst that would happen is that you would then apply the dye to the entire surface.
Finishing Tip by Bob Flexner: Comparing Rubbing Lubricants
Many different lubricants are recommended for rubbing out finishes with an abrasive. Here’s how they differ.
The more waxy or oily the lubricant the better it reduces scratching and sandpaper clogging but the slower it cuts. The more watery the lubricant the more aggressive the cutting but the more pronounced the scratches.
So wax is the most lubricating of the common lubricants suggested. Oil would be next, followed by a mixture of oil and mineral spirits.
On the more aggressive side, straight mineral spirits (paint thinner) still provides some lubrication while allowing the abrasive to cut effectively. Soapy water provides slightly more lubrication than straight water, which still provides enough to somewhat reduce sandpaper clogging.
Finishing Tip by Bob Flexner: Finishing Over Pine Knots
The resin in pine knots contains solvents that will bleed into and through most paints and finishes. This can cause the paint or finish to remain sticky, and it can cause the orange color to bleed through as shown in the accompanying picture of white latex paint applied over pine.
There are two types of products on the market that will block this resin: white pigmented primers and clear shellac. The most well known white primers are Kilz and BIN. The best clear shellac to use is Zinsser SealCoat because it has very little color and a longer shelf life than other shellacs.
Kilz and other brands are available as oil-based and water-based. In comparative tests I’ve found that oil-based works better at blocking the resin than water-based. But the most effective blocker is shellac, both clear (SealCoat) and white-pigmented BIN.
Once you’ve applied the SealCoat or BIN to the wood, you can apply any paint or finish over it. As long as you haven’t sanded through, this first coat should block the resin.
Finishing Tip by Bob Flexner: Filling Pores with Sanding Sealer
It’s generally better to use a dedicated paste wood filler (pore filler) to fill pores than the finish itself, or sanding sealer, because finishes continue shrinking. This will cause the pores to noticeably open up a little after a few weeks or months.
But you can use the finish for filling, especially if it’s water-based because water-based finishes sand fairly easily and don’t shrink as much as varnish and lacquer. Apply several coats, sand them back using a flat block to back your sandpaper, and continue doing this until the pores are filled.
Varnish and lacquer are more difficult to sand because they tend to gum up the sandpaper. Here’s a trick to make the sanding easier and make it less likely that you’ll sand through.
First apply a coat of the finish, varnish or lacquer, whichever you are using. Follow with several coats of varnish sanding sealer or lacquer sanding sealer. Sanding sealers sand much easier than the finish itself, which is the reason they are sometimes used for the first coat.
Then sand the sanding sealer, as shown in the accompanying picture, until you feel the resistance of the coat of finish at the bottom, which is the varnish or lacquer. Stop when you feel this, clean off the sanding dust and decide if you need to apply and sand more coats of sanding sealer to fill the pores level.
Finally, apply several coats of varnish or lacquer to finish up.
Finishing Tip by Bob Flexner: Polyurethane and Sealers
Oil-based polyurethane is a very durable and hard-curing finish. It bonds well to itself, especially if each coat is sanded a little after it has dried well enough so it powders. This creates fine scratches, which improve the bonding of the next coat.
It’s a good idea to do this fine sanding between coats anyway to remove dust nibs.
But polyurethane doesn’t bond so well over finishes marketed as sealers, especially over sanding sealer. This sealer is good for use under non-polyurethane varnishes because regular alkyd varnishes gum up sandpaper. So to speed production, a sanding sealer can be used for the first coat. Sanding the first coat not only removes dust nibs. It also removes the roughness caused by the swelling of the wood fibers.
Shellac can also be used to seal wood under polyurethane. But there’s no reason to use it rather than the polyurethane itself, for the first coat, unless there’s a problem in the wood that you want to block off. Problems include pine knots, silicone from furniture polishes (which causes “fish eye” or “cratering,” especially on old wood that is being refinished), and odors from smoke damage or animal urine. For these cases, applying a first coat of shellac usually blocks off the problem.
If you do use shellac, you should use the dewaxed variety. The commercial product, available in home centers and paint stores, is SealCoat. Or you can buy dewaxed shellac flakes and dissolve your own in denatured alcohol.