Michael Dresdner » finishing techniques

Hand applied sunburst

Michael — Fri, 03 Dec 2010 14:00:12 +0000

Q: How do you recreate the look of the old style hand applied sunburst used on Gibson mandolins from the 1920s and 1930s?
A: The somewhat rough look of the inside ring of the sunburst comes from the old style hand applied sunburst as opposed to one that is sprayed on. It’s a moderately difficult technique that I described in an article I wrote back in the early 1980s in Vintage Guitar Bulletin. It involves working dye from the outside in onto a surface already fully wet with the solvent of the dye, to prevent it from grabbing too much.
For example, with water soluble dye, you start with a fairly weak dye mixture and a top fully wet with water. You work with two rags; one wet with solvent and the other with dye, and apply and wipe successively, creeping up on the color as you go.
Once the inside color is where you want it, remix the dye to a stronger concentration of the same color and do the same thing, this time staying closer to the outside edge. The first dye blends into the undyed center, the second blends part way into the first dye, and so on. Do as many color gradations as you like and need.
It takes some practice, and is one of those things that is hard to describe. It’s easier to learn if you actually get to see someone do it, which is why I have thus far avoided posting about it.

Gaps away

Michael — Fri, 26 Nov 2010 14:00:30 +0000

Q: My floor looks good but there are some small gaps between the floor boards. It is an oak herringbone floor with a polyurethane finish. What is the absolute best product to use to fill the existing gaps?
A: In my opinion, it is trowel filler or pore filler, depending on the size of the gaps, but those are meant to go on before the finish, or at least before the last coats of finish. There are several good brands out there, but my favorite is Timbermate, which works as either a trowel filler (thicker) or can be reduced with water to work as a thinner pore filler. Again, that is a filler that is easy to use, but must have finish put over it.

Pen polish

Michael — Mon, 08 Nov 2010 14:00:07 +0000

Q: I am new to pen turning. Can you recommend some finishes?
A: It depends largely on the pen material. Obviously, cast acrylics need no finish and can simply be buffed. Ditto for very hard or resinous woods, like rosewood, ziricote, bocote, cocobolo, lignum vitae, ebony and even boxwood. For other woods, I tend toward simple finishes; just wax, or wax over boiled linseed oil or wipe on varnish. For a very durable finish, I also like either cyanoacrylate (CA), or a combination of boiled linseed oil and CA. The CA will instantly cure the oil into a hard solid film. Using paper towel applicators on the spinning lathe, apply a thin coat of one, then the other immediately. Add as many coats as you like, sanding for smoothness when necessary. Once cured, which takes only minutes, this finish will buff nicely.

Crisp masking lines

Michael — Tue, 02 Nov 2010 14:00:56 +0000

Q: How do I achieve a nice crisp symmetrical line when using two different stains? For example I want to stain a light triangle inside a dark rectangle. The stain has bled under the painter’s tape in my tests.
A: There are a variety of techniques, but they depend on both the type of stain you are using and the type of wood. Without knowing both, I can’t advise you of the best course of action. Here’s just one of the many ways to approach this that works well with fairly absorbent wood and pigmented stain.
Stain the lighter color over the entire surface. Mask off what will be darker, and seal the light triangle with a sealer that will not dissolve with the solvent in your darker stain. Now reverse the process; mask off the light triangle using either lacquer tape (typically green) or pin striping tape, (typically olive). Now add the secondary dark stain to the exposed areas. The combination of the correct tape atop a sealed surface should prevent the dark stain from creeping onto the light area, and still give the look of stained wood rather than a tinted finish.

Inked salad bowls

Michael — Fri, 29 Oct 2010 14:00:31 +0000

Q: I want to color walnut sapwood on salad bowls with India ink, then seal it with shellac and salad bowl finish. Would this be safe for food?
A: Yep. By the way, I would let the ink dry then go straight to salad bowl finish. In this case, adding shellac would weaken the finish.

Timbermate as pore filler

Michael — Thu, 28 Oct 2010 14:00:04 +0000

Q: I plan to paint oak cabinets. Someone suggested Bondo for pore filling but I am considering Timbermate instead. Any tips on grain filling with that product?
A: For the record, polyester body fillers like Bondo will also work just fine as pore fillers under painted surfaces. As for Timbermate, simply thin it with water to whatever is the best working consistency for you. I like it about the consistency of heavy cream for pore filler work, but you may prefer it a bit thicker or thinner. Fill, let it dry completely, and sand. It’s very simple and there are no hidden surprises. Incidentally, it will work over both raw and sealed wood.

Drifting along

Michael — Wed, 29 Sep 2010 14:00:47 +0000

Q: How can I produce a driftwood finish, like the one in this picture? I am thinking of using bleach, chemical stains and dye rather than paint or pigment stain.
A: I have to say that the photo you sent looks nothing like what I would call driftwood. In fact it looks like roughly prepared wood with open cracks and grain raised with water that has been sealed with an off white toner, wet glazed with burnt umber, then topped with dead flat clear; a rather classic antique finish. If that is what you want, that’s how to recreate it. If, on the other hand, you want driftwood, try this.
Raise the grain by flooding the wood with water, wiping off the excess, then leaving it overnight to dry. Add cracks if you choose, or distress marks, if that is what you like. Mimic erosion by scrubbing the wood aggressively with a wire brush. This works best on softwoods whose early wood bands abrade more quickly than tougher late wood ones. Add black and off white paint to their solvent to make a quick stain, but mix only perfunctorily. A piebald gray is the goal here. Wipe the paint onto the wood and off. You should have areas of lighter and darker gray that looks similar to real driftwood.

Lacquer and d-limonene

Michael — Tue, 14 Sep 2010 14:00:40 +0000

Q: I need to know if d-limonene will harm cured nitrocellulose lacquer. I want to use it as a solvent in a 25% mixture with mineral spirits.
A: No, d-limonene will not harm lacquer. It is one half of the racemic mixture called dipentene, and for all intents and purposes as far as finishing and cleaning are concerned, it is completely interchangeable with mineral spirits. There’s no difference in how they behave. The only real difference would be price due to derivation; inexpensive mineral spirits comes from petroleum, while the decidedly more expensive dipentene is extracted from citrus fruit peel.
In case you were curious, the d-, which stands for dextrorotatory, or right hand rotation, is generally lower case in chemical notation. It’s fellow traveler in the racemic mixture is l-limonene, for levorotatory. Racemic mixtures contain equal amounts of left and right mirror image versions of the same molecule.

Anti-acid?

Michael — Mon, 13 Sep 2010 14:00:59 +0000

Q: We are getting an increasing amount of mineral calcium deposits in rosewood. Do you know of an effective way to remove them, aside from the acids that are currently available?
A: No, but to be honest, muriatic acid, which is cheap and easily available, works so well and so quickly with most mineral deposits that I never bothered to look for an alternative. The fact that acids, unlike bases, do not discolor most woods keeps it the favored choice for that problem.

Open pore or filled

Michael — Wed, 08 Sep 2010 14:00:12 +0000

Q: I would like to use the shellac and wax finish we learned during the uke building class on a classical guitar I built, but it’s Indian Rosewood and the pores look a bit open. Do I need filler first?
A: The finish you used on your ukulele is a very thin, open pore finish. It will also work on a guitar made of open pore wood, though the pores will remain open. That in itself is not a problem; it is an option. If you like the look of an open pore finish, and I must admit that I do, there’s no reason to fill the pores.
If, on the other hand, you want the pores filled so that the surface looks more like glass than wood, you’ll save a lot of time and effort by filling the pores with pore filler before layering on finish. I should point out that pore filling is usually paired with thicker, multi-coat built up finishes that get rubbed out to gloss, not with thin, natural looking flood on and wipe off finishes such as what you have on your ukulele.