Okay people, here's what I've learned from using General Finishes Enduro Var. Hope you are ready for a bit of a read - I took my time, and wrote this up rather carefully.
The bottom line message: To bring Enduro Var to a fine polished surface, you need to do everything during the first 10-days after first application. That first coat starts the clock ticking, and in that first week the finish is amazingly easy to work with. After the finish has cured, it is still reasonable, it is just a lot more work to polish.
Some Basics:
It is overall an easy finish to apply. I used an HVLP gun for the guitar, used an air-brush and artists brush for some touch-up, and prior, I used pads of paper towel to do my test piece. All worked great. Never used the foam brush that has been recommended but I’m certain it would work well.
My Gun: HVLP, gravity feed, touchup (small cup), 1mm tip, all stainless/brass internals. I ran at ~20 psi, and although the finish seems relatively high viscosity, it atomizes just fine (I assume it has very low surface tension - but don’t really know the fluid properties)
Schedule:
I screwed up - pretty bad I think. Let me outline what I did, then quickly update on my ideas to improve
What I did:
- Sanded wood through P220 on a random orbit sander. Per directions
Sprayed on bare wood (per instructions) one straight coat (not thinned - instructions recommend thinning with water - no way - too much water! More on this later)
Applied one coat of Cryslat Lac pore filler
Sanded back to wood with P320
Sprayed 2 more coats that weekend
Had a problem with blotchy color on the heel - so decided to work on sanding the heel back to wood - sealing with shellac - and recovering the heel
Fixed drips/sags by scraping/sanding
I was delayed in spraying again because of poor weather till the next weekend
Sanded surface back to flat(ish)
Sprayed 4 coats a week after the first 3 coats
The finish seemed so thick I decided to stop - even though S-M directions say to do 6-8 more coats at this point
At this point, I did some minor touchup of some thin spots on the heel I has re-coated
I then put the body and neck into my hot-box for a week (8 days really) to cure
Then I started sanding back to flatten the surface - I started flattening the surface with 800 on a hard block
I then moved on to P1200 and had hoped to be able to buff with medium Menzurna - that had worked on my test piece - no dice
Buffing on a fully cured surface that has been sanded with P1200 paper looks like … well I’ve never seen a finish that looked like that - it was a hazy blue, almost opaque finish - frightening
I figured I had let it cure too long, and it just needed wet sanding to a finer grit before I could buff it out - Micro-mesh to the rescue! If Micro-mesh can bring an F-18 canopy to optical clarity, then I think it can tackle this
Wet sand with Micro-mesh 3200, 3600, 4000, 6000, 8000 (checking at each grit to see if it would buff)
Buff medium and fine Menzurna - done (whew!)
What I should have done (I think):
- Apply all coats within 2-3 days
Allow finish to cure for 3-5 days at room-temp (not at elevated temperature!)
Flatten and polish
My test sample buffed so amazingly easy, I’m pretty sure that before the finish is fully cured it burnishes very easily - that is where you want to be when polishing this finish. Once it is cured (cross-linked) it is crazy tough (As predicted by folks here). This is the only finish I’ve ever worked with where I had absolutely no fear of sanding through. Having only ever worked with shellac and nitro - this is a new experience for me.
Pore filling:
The Crystal Lac pore filler I used really did nothing to fill the pores, and required me to carefully sand the whole thing back. That was a waste of time - and it could have contaminated the
The fantastic thing about this material is that it sands to a nice dry powder just hours after application. It almost never corns on the paper at all. Also, it shrinks back very little after the first day of cure. So the best way to fill pores (IMHO) is to use the finish itself and sand back while the finish is soft and easy to work. Maybe shellac and pumice would be a good pore fill - not sure about that yet tho.
Sanding:
As I said, when fresh, it sands easy and it does not load the paper - GOOD!
However, as the SM instructions state, overcoating finish that has been sanded with grit coarser than ~P1000 shows the sanding scratches through the new coat - even through a very thick coat. I think I know what is going on here - the finish pulls away from sharp edges when it cures - more later.
The good news is that even orange-peel is pretty easy to flatten with P800 - then you can hit it with P1200 and the scratches will be hidden
Pull-back from edges:
As I just said, I think the finish layer has a tendency to shrink as it dries and pull back from un-constrained boundaries like the hard edge of a headstock, tuner holes, or even deep sanding scratches (apparently). There is no way that a scratch from P400 grit paper should be visible under a heavy coat of this stuff, but it will show like a sore thumb - I could be wrong.
The pull-back seems to happen as the thick coat is still losing water, and there is only significant “wet” time with a heavy coat. If you can get a fully covered thin coat, the water dries off so fast, that there is no time for the coat to pull back.
SO - thin coats are the trick with headstocks, or the face of a solid-body with PUP cut-outs and switch/pot holes (HA! potholes)
Drop filling:
This stuff drop fill excellently! It is relatively high solids content (relative to nitro), AND a 1-day old drop-bump is easy to flatten. Makes for perfect drop-fills
Also, on the cured finish, CA will drop-fill almost invisibly, so any last minute bo-bo’s can be quickly and easily dealt with.
Spraying is a delicate balance:
Heavy coats work fine on large featureless surfaces (like back/top/sides), however, the heavy coat will stay “mobile” for a long time - it can kinda’ slide. If you do not cover completely, you get the “deep orange peel” problem see below. So get your Goldilocks mojo on, and spray coats that are juuuuuuuust right. Heavy is better for large plates where it will not pull from an edge - because any drip or sag is still easy to flatten, and the finish will cure once the water has dried off.
The “Deep Orange Peel” problem:
This happened to me a couple times and it is easy to deal with once you know what’s happening (I expect this happens with other finish materials, but I’ve not experienced it).
If you spray just too light (or heavy but splattery), this finish can create an orange peel surface that has very deep pits where the dimples are. If you then go back and re-coat without fully sanding flat, the dimples will hold tiny bubbles and it will create a freaky blue haze that is deep in the finish. It is like a blush, but under magnification you can see that it is created by distinct bubbles that are regularly spaced. So - cover completely, but when you don’t - flatten it!
Must seal endgrain with shellac:
Having used waterborne finishes decades ago, I am very familiar with the technique of sealing end-grain with shellac, otherwise the waterborne finish will leave an ugly blue blush. I was overly optimistic that this finish had solved that problem, WRONG!
I should have thought about it more, because I’m pretty sure this is caused by the water swelling the endgrain pores shut - the finish can’t get in - and when it dries, the unfilled surface shows as a blush. This finish has water - so it’s going to happen - no way around it.
General Finishes very clearly warns against applying Enduro Var to anything except raw wood, so I decided to do just that - I should have tested.
They do say that you can cover over a shellac seal coat if you sand back to a wood outer surface. Well, that seems to work fine.
It may be best to do a thorough shellac sealing for all surfaces - I will be testing this once this guitar is delivered.
Some random things:
The Coco I finished on this project has some very dark resinous areas in the wood. These areas had different surface properties of the finish than on the surrounding wood - so there are some lines that outline these regions on the final finish. This is probably because the resin hindered the cure, and the finish is softer over these areas - not a big problem at all.
Rob Collins has a valid concern about using a waterborne finish on the super-thin plates of a Uke. The wet first coat made some hide glue joints swell (visibly), and the back plate of this guitar creaked audibly when I applied the finish (I see no cracks now). I think it just moved very fast. I think a thorough shellac seal-coat will help with wood swelling, but I’m not sure it will keep exposed hide-glue lines from swelling. This is a concern for me.
The finish is a freakish pink color in the can - the cured film is an attractive amber, but it looks like pink lemonade that has been thickened with cornstarch. Not a real concern, but … really.
I got some witness-lines that I could see when the finish was matte (while sanding). I expect these are between layers that were applied a week apart. Fortunately, they do not show on the buffed surface at all. So no big deal.
Ebony binding looks outstanding under this stuff (IMHO). As you can see in my pictures, the color variation in ebony can actually be seen under this stuff, unlike nitro where it just turns jet-black.
Bottom line - Will I use this finish again?
I think so. Nitro is just so nasty, and shellac is so tender, that I think it is worth the learning curve. This job looks and feels good now, but I want to see if it is received well by the shop I sell through (SBGB), and if it stands the test of time (which I expect it will).
The big improvement for me would be if I can seal the entire instrument with shellac and not have to worry about adhesion issues. I think the spruce will look better with a shellac barrier coat, and I think it will be essential for any curly-grain wood.
