Lacquer Holes Along Binding

[Steve Hinde]

I've been finishing a few instruments lately and one thing that really drives me crazy are the craters along the binding in the lacquer finish. I wipe the instrument down with alcohol after prep, but still get the occasional crater. Should I use Naptha or mineral spirits or Acetone? I am worried about finish adhesion. It has to be the glue or the binding material itself. I use the LMI binding adhesive. I intentionally put on 3-4 coats along the edges for additional build, but the binding lines almost always look low compared to the adjacent areas. Wide lines are ok, but the laminated lines are the biggest problem.
I spend a lot of time touching up and would like to have clean edges around the first time. Fish-eye flow out or what? If you use it, you need it in every coat?
I get all the work done and get really frustrated when it comes time to finish. Patience and detail also play into that one.I am getting better at the techniques, just want to get over that last 10%.

Steve

[sunburst]

Any gap of any size along the edge of the binding will show up as a "crater" when you apply lacquer over it. Perfect joints around the bindings eliminates those, but as we know, we can't get them perfect always.
I usually drop fill those occasional "craters" with thick lacquer. I put some lacquer in an air brush bottle and let it sit out for a while so some of the solvents evaporate and it thickens. Sometimes I fill stuff like that with stick shellac and a burn-in knife.

[Steve Hinde]

Thanks John

That is exactly how I touch up the issue. I have a bottle of thick lacquer I use, sometimes with a little lacqer melt to blend after the fill if necessary. Scrape it down with a razor blade, sand a little and continue on. I don't see the gaps though. It looks like a contaminant like silicone or from the binding glue. Like the lacquer is 'repelled' from bonding. There is no material in the bottom of the crater. I am tempted to try a little grain filler around the edges first to see if that helps. Can't be any worse than sealing wood binding. A little brush and a little patience. Would probably take less time in the end.

[sunburst]

What kind of binding and what are you gluing it with?

[Steve Hinde]

I am using celluloid nitrate and the LMI contact cement FCA. I used to use their binding cement FGW, but I like the application of the FCA with a brush or syringe. I can work a little at a time and put the adhesive in where I want it. It also seems that I have more issue with the black/white/black than the iv/black/iv laminations for some reason. Plus the black layers can ignite before the white or ivoroid when I warm it up. I take a lot more care when I use that material. Maybe there is a difference in the black vs the other? I can see where the lacquer runs down into a gap. But some of them just look like a contaminant. I'll try to shoot a picture when I get home Friday.
The craters are not excessive, it is just a frustration to continually have to deal with. It is probably just gaps as you said, with more of the adhesive exposed, maybe there is some interaction going on that doesn't happen when the glue line is tighter. I look very hard at the gaps before I put on the first coats, all looks good, then oops, there's another hole. Maybe I jst need a stronger prescription. It would be nice to put on the finish and for once not have to fill a hole somewhere.

[Mark Franzke]

I think it could be the lacquer solvents that might shrink the binding a little. I'm no chemist, but those little pin-holes always seem to form where the binding meets the wood. I always scrape the bottom edge of the binding to a slight bevel before I glue it on, so there is no visible gap. I use clear McFadden's pore filler before I stain, especially working it along the binding edge. Then I sand it completely off. It's hard to tell when you've got it all sanded off, but if there is any residue, it will resist the stain. After spraying, I have minimal drop-fill issues.

[Jim Hilburn]

There are several issues about getting binding to fit well especially along the sides.
First is having the sides and top square to one another. I use a straightedge to make sure I'm not doming on the sides. Then try to make your rabbet cuts as square as possible. I use the LMI cutter with bearings on a router table with a riser and cut just short of rim joint. This leaves a little wood to remove by hand to get down to the rim and this is where I often have trouble. With a good glue joint it's difficult to know then you've arrived. You have to watch for the change in grain. Don MacRostie uses a wax pencil along the rim so the top doesn't stick well there and makes them separate more cleanly. But this is where you have the most chance of damaging the wood at the binding joint. I'm wondering if it might be better to go ahead and try to remove all the top wood with the router but then you really need to have your top edge thickness right on all the way around. I know the rim is a constant.
The next problem is how do you clamp binding into the rabbet? It's always been tape or rubber bands but in any case you are primarily putting pressure on the top outside edge and really don't have a good way to press the binding tightly in at the bottom. For me this routinely means the binding sits in the ledge pulled very tight to the top where I seldom have any gap problems but is not forced tight in the bottom no matter how much finger pressure I try to use as it's going on. This obviously can lead to a gap since the binding is square but isn't squarely in the square rabbet. If you can figure out how to trim the binding on the bottom evenly with a little less than a 90 you can probably get a better fit. And if anyone has a great idea for adding more inward pressure to the bottom of the binding as it's being glued I'm all ears.

[Rroyd]

I used a small wire (1/16 maximum) that pushed in on the bottom of the binding, so that the rubber banding pushed downward on the top of the binding and pushed in on the wire to hold the bottom tight as well.

[Lefty Luthier]

My best guess is that the thinner in most sprayed lacquers works into the glue voids along the binding edge and when it dries, leaves those pesky craters. Drip filling with thick lacquer is the least complex fix and then sand smooth.

[Dale Ludewig]

There is another help here. If you're using celluloid binding, put it in some acetone and make some glue out of it. It's not going to fill the little holes and such, but it will do some amazing stuff. Nothing will substitute for good craftsmanship.

[Steve Hinde]

Most of what I am seeing is along the top between the binding and the top wood. Almost never along the sides. I usually don't use any grain filler on the top. It might be time to use it along the binding on the top, just for these gaps.
A lot of this is my mental block and attitude towards the finishing process. It is something that I need to get better at. Like everything else, the more I do the better I get at it.
As always, if I have questions, I can ask and get some great responses here. Thanks for the replies.

[Michael Lewis]

Small gaps along the binding are best filled with something that won't shrink, sink, or swell. My usual choice if a filler is needed is CA glue, because it sets up well within a few hours and stays pretty much the same from then on. Lacquer fills tend to sink over time, and epoxy can swell with sweat and other moisture.

Most of the work of a finish job is in the preperation, then the actual application of the finish goes smoothly and quickly.

[Steve Hinde]

Michael,

I thought about that too. You would have to do it after the seal and leveling coats. It could cause some problems during staining. I would hate to sand or scrape through when leveling the CA.
You are all right on the money, finish is entirely dependant on the quality of the prep work.
Again, thanks for the responses.
Keep wit lin....I am

Steve

[Michael Lewis]

This goes to your level of workmanship. Stay focused and pay close attention during each step, and you should have less and less to contend with at the end of the whole process. As long as you know how it should turn out (to quote Captain Picard) make it so.