Lacquer + Preval Question (Refinishing the Purple SSB)

[davegardner0]

Well it's been a year and a half since I completed the SSB bass in my signature, and it's seen a fair bit of use. Unfortunately the shellac isn't holding up too well under gigging conditions, so now it has some finish damage in the forearm area.

I'm thinking of drop-filling and scuff-sanding the shellac, then finishing the whole body over top with nitro lacquer. I've completed some test pieces using Minwax spray can lacquer so far and they came out really well. But for the real deal I'm thinking maybe it would be better to use a Preval sprayer instead of the spray cans. (am i crazy?)

I've used a preval before spraying shellac to seal in aniline dye, and it worked really well. Plus I can use whatever lacquer, thinner, and retarder I'd like and have more control over the process in general. On the other side of the equation, I like the compactness of the whole system vs. a compressor and spray gun. The quick and easy cleanup is nice too.

So I'm wondering, has anyone here finished an instrument with a Preval? Any opinions or tips for spraying clear lacquer with one? For instance what sort of lacquer should I use? Also how should it be thinned to spray through the preval, and what thinner do you recommend?

Here's how the bass looks now, by the way.

 

[Cagey]

I don't have a great deal of experience with the Preval units, but what I have noticed is they're sensitive to viscosity. In other words, don't try to spray a sanding/sealer material, as it's usually much heavier than lacquer, which is typically reduced quite a bit.

I moved to an HVLP unit some years back, as they're also pretty compact and relatively inexpensive compared to traditional HP systems where you need a compressor, filters, regulators, dryers, hoses, guns, etc. and the space to store it all. Also, you get less overspray/waste, while still getting stellar results. If you think you might be doing several more bodies over the years, it might be worth checking out something like the Earlex 5500. They can usually be had in the $250-$300 range, and that's your entire expense.

 

[mayfly]

It's not that bad.  Why not just keep playing it?  IMHO and all that...

 

[aarontunes]

It's not that bad.  Why not just keep playing it?  IMHO and all that...

Right! Some people pay extra for that.  :glasses9:

 

[davegardner0]

Yeah I did think about that, but it's my wife's bass not mine. So it's her choice and she really doesn't want to break through the color coats. And the whole body does look shabby, lots of other small dents and stuff. So we'll fix it up, should be fun!

 

[Cagey]

Women. Can't live with 'em, and you can't shoot 'em.

 

[BigSteve22]

Women. Can't live with 'em, and you can't shoot 'em.

Can't tell you how many times I've used that phrase!  :headbang:

 

[Cagey]

I thought my brother came up with that observation after one of our dingbat neighbors in the old 'hood went to prison for testing that truism, but a Google search shows it's been around for a while. I guess I shouldn't be surprised - its not exactly a new sentiment...

One of these days Alice—POW! Straight to the Moon!​

 

[rgand]

I've used Preval sprayers several times to touch up the paint the on an airplane I had. One time it was a fairly large area. They worked great for that and Imron should be a similar consistency to what you're planning. Just practice on something first to get the feel of the spray tip so you don't put too much on.

 

[Cagey]

I shot a few vehicles with Imron many moons ago. Lovely stuff. I don't remember it being particularly thin, but it did sag easily so it probably was. Of course, lacquer would also sag easily if it didn't practically dry coming out of the gun.

 

[davegardner0]

Here's a better view of the damaged shellac. I've already drop-filled all of the pits and scratches with shellac, and scuf-sanded the body smooth.

[youtube]https://www.youtube.com/watch?v=njfMaERXsnY[/youtube]

For the record I'm also in favor of fixing the finish. I'm not a huge fan of the relic'ed loo, plus this doesn't even look like normal wear.

 

[Cagey]

Reminds me of the random scratches you might get on the back of a guitar from a belt buckle or zipper. Does she wear jewelry or a watch or something on her right wrist? Need to identify the source of the damage or it's gonna do the same thing to lacquer.

 

[davegardner0]

Reminds me of the random scratches you might get on the back of a guitar from a belt buckle or zipper. Does she wear jewelry or a watch or something on her right wrist? Need to identify the source of the damage or it's gonna do the same thing to lacquer.

It's definitely not jewelry causing the marks. Although they look like scratches, I think the cause was more chemical/heat related. It's hard to see in the photos but around each trench there is a "crinkle" texture. Plus in person they don't exactly look like scratches. And there's similar markings wherever the bass is touched while playing, not just on the arm rest. In the video you can see one where the right hand thumb goes, for instance.

My theories of the possible cause are:

• Heat and humidy while playing softened the shellac
• I've read that some people's sweat can dissolve shellac
• It's possible that the initial shellac I sprayed to seal in the dye was too old and didn't cure properly. I used spray can shellac and the can wasn't dated.

So if it's the 3rd option, obviously that's really bad and maybe unfixable without a full strip down to the wood. It's possible that the same damage will come back once I put the lacquer over top. But, I really don't want to strip and re-do the purple burst dye if I don't have to. So I'm willing to accept the risk, and I'm only risking the time and effort of applying the lacquer.

Also this is why I've switched to the Preval for spraying shellac to seal dye - I mix my own from flakes so I know exactly how old it is.

I've already drop-filled and scuff-sanded the body, and I'm planning on letting it sit sanded for weeks before spraying the lacquer. So hopefully sanding will open up the shellac and let it cure further if it needs to.

 

[Cagey]

I thought those pics looked a little more wrinkly than scratchy, but it's hard to tell sometimes just from pics.

There's a reason very few commercial manufacturers use anything other than polyurethane for finishes: durability. There are other good reasons too, such as ease of application, appearance, end cost, etc. but that's at the top of the list. Lacquer comes next, but it's labor intensive so it's not used much these days, either. Unfortunately, for various reasons, shooting poly is outside the purview of most DIY-types, so lacquer is the thing to use. Anything other than those two finishes is just too flimsy. The amount of physical abuse and the variety of compounds a finish might be exposed to just takes everything else out of the running.

 

[Seamas]

I thought my brother came up with that observation after one of our dingbat neighbors in the old 'hood went to prison for testing that truism, but a Google search shows it's been around for a while. I guess I shouldn't be surprised - its not exactly a new sentiment...

One of these days Alice—POW! Straight to the Moon!​

Alice was friggin' cute.
Should have shown Ralph the door.

 

[Cagey]

Should have shown Ralph the door.

Except back in those days, a single woman didn't have a whole lotta options.

 

[davegardner0]

Stew-Mac sells preval units and of course also lacquer, so I tried emailing them for advice on how to use them together. They told me it should all work well together. They recommended a 50/50 mix of lacquer and thinner as a starting point, and see if it atomizes properly. So, I ordered their lacquer and thinner, plus some retarder if I need it. We'll see how it goes!

p.s. I never replied properly but I looked into that Earlex 5500 spray station. That's really cool! I think for right now it's a little overkill and more than I want to spend. Plus I have extremely limited storage for equipment. But on the other hand if I end up doing more finishing I could definitely see myself thinking about one. So thanks for the info!

 

[davegardner0]

Well I was able to get a few "warm" days at the end of December to spray my bass body, and it worked pretty well! The preval worked well - I used a 50/50 mix of lacquer and thinner, with 10% of the thinner replaced with retarder (stew-mac's recommendation). I felt like I had good control of the finish thickness going onto the body, and I didn't really get any runs over the course of approximately 12 coats.

Of course the only downside is that the preval does leave a bit of a "rough" finish with some orange peel. So that'll be more work when sanding out to a gloss. But, I think I have a good finish thickness at this point and it seems to have cured well.




It's been about 4 weeks since spraying, so I'm thinking I'll start the rubbing out process soon!

 

[Rick]

Meh ... what's normal wear?  Looks like character.  That said, if she wants to have it refinished, no biggie.  Just go for it.

 

[davegardner0]

So I started wet-sanding the body today using 600 grit paper and soapy water. All was going well until I noticed some nasty cracks around my control pot holes, and some smaller ones around the pickup cavities  :icon_scratch: ???

I'm wondering if water got into the exposed end-grain? I'm really surprised though, I definitely painted the inside of the pot holes with shellac when I did the original finish, plus it would have got a bit of lacquer spray into the holes too.

I'm not using that much water for sanding, but definitely enough to do this to un-finished wood for instance. But if I use any less the paper seems to "stick" to the body pretty badly.

So...ideas on how I can fix this? I'm afraid if I proceed as-is the cracks are going to show after buffing the final finish. Plus the could get worse as I go through the grits.