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Well, this applies to Nitro also. But WHY do I have so much trouble with drop filling? If I put a drop on a flat, finished area, it will flatten out to a bump, with some depression in the middle. Now, if there is a small, open pore, then it almost ALL dries to a "ring" around the pore... the hole never seemingly wants to fill. OK, it will after MANY apps, but there has got to be a secret I am missing (other then better pore filling before finishing).

Anybody experience this? Anybody have good ideas?

Mike

It sounds to me like the "pores" you're trying to fill are fisheyes instead of pores, caused by some kind of contamination that was in/on the bare wood.

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I didn't mean to say it, but I meant what I said.
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It's possible Mike that you may need more than one drop at a time depending upon the size of the spot to be drop filled.
I will often use two or three drops at a time even if it looks like only one is needed, and let it settle in for several hours before
leveling. I'm not sure about how this works with the EM6000 (though they claim it works similarly to Nitro). But it has always
worked well on Nitro for me.

Temp and humidity play a great role too. I have used Hot Hide glue to pre-seal spots that I thought may have a problematic
pore as well. As Todd said in another post, those little men working in the pores are always working against you.

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Bill Hodge


One does not simply, own enough guitars!

Hot hide glue? That makes sense. I tried CA, but the sanding required to level is much too agressive considering there is a finish already laid down. Be nice if Target made a "burn in" stick of the stuff, eh?

Mike

Mike, your description of drop filling sounds about normal. The lacquer shrinks a lot while curing, so it will continue to sink down into the depression until it finally builds it up. I use the ring that is created from the first drop fill to contain additional drop fills. Watch the center. When the pin hole finally stays filled, then you can let it fully cure and scrape it flush. Sometimes it takes three to five drop fills to fill a deep depression.

I have switched from "dropping" to brushing light coats of slightly thickened lacquer into the depression with a fine artists brush. I do an application every hour all day long as I do other work in the shop - 10-12 coats in all. This method seems to work better for me as I seemed to be too timid in flattening the bump I got from dropping and it would always show after buffing.

Chuck

This all sounds very much like my experience. BTW, there is no fisheye problem here. But there is a strange effect and that is how a pore seems to effect the middle of the drop. No pore, no serious ring build up. Got a pore, the ring gets bigger. Wierd.

How do you thicken the lacquer? Let it set out? Warm it?

Mike

No mystery here. The affect you are seeing is called surface tension. We have all seen a drop of water hanging on the end of a straw with out falling off. The higher the specific gravity of a liquid the greater the surface tension it supports requiring more mass IE gravitational force to overcome the specific surface tension. What is happening is the finish as it evaporates its solvent is gaining specific gravity and therefore surface tension and it is clinging to the walls of the cavity as it cures out. Because of this as it shrinks back it leaves a recess in the center.

Mike,
I put about 1/2 inch into a small glass jar that is about the size of a shot glass and leave it uncovered. After about 18 hours it's a little thicker than pancake syrup and ready to go. The little jar that I use came with an inexpensive air brush kit that I use for finishing necks. After it's at the right viscosity, I put the lid on and it's good for a few days.

Chuck

Right Michael, I get that. But the pore appears to have an inordinate level of influence.

Well, since I am still experimenting, I tried something different. Apply "drops" with a brush, let set for an hour, then swirl around with the brush. That worked! No need for excessive dropping.

Mike

you over came the surface tension by swerling with the brush.

The key to a good drop fill is to leave it cure long enough before leveling so that it won't shrink back later. That can be a month or so. If the finish is new then you don't have to wait so long. It can be scraped level with a razor blade taped at both ends. Then you can sand with 1200 and buff. Here is a Frank Ford tut. http://www.frets.com/FRETSPages/Luthier/Technique/Finish/Lacquer/DropFill/dropfill.html

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Ken Franklin
clumsy yet persistent
https://www.kenfranklinukulele.com

Not to steal the thread, but has anyone experienced a halo around the drop fill after leveling and polishing? This halo is larger than the fill area and only visible from certain angles/lighting?

Chuck

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Good thread, just in time for a nitro repair I might attempt.

Is there a special "instrument grade" nitro required for a drop fill, or regular nitro from the hardware store does it too?

Thanks!

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Build log

A nod to an old thread:

I've encountered a bit of a surface tension issue with EM6000 on this first use. I pore filled with SilverTip epoxy in two applications, but it seems two coats was not enough. I'll have to add a third pore fill next time. On the back (Claro Walnut), there are several 1/4" long grain lines where the sprayed finish didn't fill; it pulled back to the edges. Around the headstock inlay, there were a few tiny pockets where the sprayed finish also pulled back.

While spraying, I noticed the surface tension effect with each coat, but the finish generally leveled out after about five minutes.

For drop filling, as a trial, I'm adding WestSystems colloidal silica as a thickener to the with EM6000. It worked VERY well on a test panel. The tiny, deep pockets of the inlay filled in two sessions, an hour apart. There were also several small, deep pockets around the rosette. The colloidal silica worked better than anything I've tried for drop filling.

I'm curious to see if the "drops" will look much different after buffing. The fill areas are so small that you likely wouldn't notice them unless you looked very closely and knew exactly where they were.

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Measure Twice,

Karl Borum

I'd be trying GluBoost fill n finish on that .

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.