Thread: Help finishing #1

Thanks for your input Mando. I'm not a great fan of spray guns myself although I have had a little bit of experience doing home auto repairs (once even metal flake using a 'little beaver' which surprisingly turned out quite well - purely by accident). Once I got terrible orange peel and that's a cow to fix, in fact never really got rid of it all. Still, I've got plenty of ply and a little bit of top back and side offcut so will try brush and spray and see how it goes. I note that a lot of 'brushers' seem to favour tapered foam brushes and use it so it runs on rather than paint it on. Might be worth a try.
I've just read Mike Doolin's detailed schedule:
Waterborne finishing
his method of leaving denatured alcohol in the pot overnight and using it to apply a light coat to assist burn in makes sense and saves having to fully clean out between each session. He's adament though that the sessions should be done on successive days else burn in is prevented even with the alcohol coat.

I think you're right though, trialing lots of different prep/finishing combinations is the go,hopefully I'll find a method just right for me!

Last night I ordered the WB lacquer and Z-poxy filler to try. The epoxy filler is probably as toxic as acrylic or nitro but I'll try it anyway. Don't know if the Z-poxy will be any good on my cedar top though, I get the impression not. The other thing that I noticed when ordering the water borne is that they report that some users have reported issues with it over Tite-Bond AR glue which is a bit of a worry as I used AR with my purfling and binding.

A mando is on my list of 'projects' so will probably picking your brains in the future!!

Os.

Normally you do not use a filler on softwood tops (western red cedar, spruce etc) as they do not have the open pores found in hardwoods.
Also you do not want filler residue where you are gluing on the bridge.

Yeah Jeff, that's what I thought but I got the Guitar Finishing DVD by Robert O'Brien and he certainly does. I think he is more interested in getting a flat finish rather than closing off the pores. He measures up the bridge position prior to finishing and then masks it up (a couple of mm short of the marks for safety) and fills with Z-poxy. The when I ordered it from LMI there is a note somewhere in their docs saying it's not suitable for cedar. Dunno, this is why I'm so confused! I've still got Dan Erlewines book on finishing coming and that will probably make things worse - there's just too much information. What I really need is for someone to say "hey idiot, this is the way you do it. Step1......". But that's not going to happen as it's clear that there are a multitude of ways to finish and a lot of guys seem to get quite passionate in extoling their method as the one!
I cut up half a dozen 300X300 sheets of ply today and will start trialling various combinations. I think that's the only way that I will get it clear in my head. I've filled the bare wood of a half sheet with Timbermaster today and will rub that back and then shellac it. I'll then use the steel wool/shellac method to rub dust into the other half and see how that goes. at least it's a start.
I also started making a jig for spraying so that I can hold the body and neck flat and rotate it while spraying (or brushing). This seems to be good advice for the beginner.

Os

Far be it from me to say Robbie is "wrong", but he is certainly the odd man out when it comes to putting epoxy on a spruce top. There was a thread on another forum recently where a new builder had used epoxy on a top and was now wondering about bridge adhesion(he had not masked)
The overwhelming consensis was that epoxy on tops was a really bad idea, unless you were doing something like a mahogany top.
I would not put steel wool anywhere near blackwood, it reacts with iron and moisture to produce black stains

Mike Doolin (link above) is another that fills the soundboard with epoxy (link above). That is where I read about the problem with cedar - he says it goes blotchy, and advises a thin spray coat of shellac (I guess 1lb cut) under the WB. Is this a good method? or would you just spray the WB straight on All in all though, I think you are right, by far and away the majority don't fill the top plate as near as I can tell so I'll do the same. Thanks for the advice on the steel wool, that's really good to know so I'll staty right away from that method. I think I've decided to wait till the epoxy gets here from LMI and fill the back and sides with that although it appears that it doesn't adhere to shellac (and vice-versa) so will have to make sure that if I go the shellac route on the soundboard I don't get any on the sides. I've ordered a 1.4mm Star gravity feed HVLP gun so between that and my standard gun I should get a feel for whether spraying will work for me.
Bigger problems last night though. I managed to get some swarf on my bench when finishing off my spray jig and put a couple of decent scratches and dents on the soundboard. I was going to try the 'steaming out with an iron' method. Is this the best way to go? Just a stupid slip in concentration and lack of forethought. Gotta be philosophical though, a valuable lesson learned!

Os

Bummer about the scratches and dents, dents steam out well scratches where the fibres are torn will probably need to be sanded out.
I use a big flat tipped soldering iron and wet folded over paper towel.
I have little experience with waterborn finish, but make sure your shellac is de-waxed.

I have just been doing some more research, and as far as water based finishes go, the one that seems to be getting the best reviews at the moment is KTM-SV. This is not an acrylic so does not have the blue tint problem. It is an alkyd resin urethane, similar to Target Coatings EM2000 that I use on my mandolins, but it is harder than EM200 and is reported to be easier to spray. EM2000 is a very clear finish, but is tricky to apply and you can scratch it with your fingernail. The only problem with KTM-SV seems to be is that it is sensitive to oily woods, so you do need to make sure the surface is sealed before applying the finish. You can use dewaxed shellac or Zpoxy or some other sealant to do this. It is supposted to be brushable, but I can't find anyone who uses a brush. Alkyd resin I believe is a modified oil and oil finishes do not usually have problems with sweat damage. I have not damaged any of my mandolin finishes so far with sweat from my hands. On the other hand, a shellac french polished finished that I used to use years ago is easily damaged by sweat. KTM9 has had problems with sweat damage and is not recommended by some guitar makers because of this.

I have some KTM-SV and KTM9 in the mail from LMI at the moment and will be practicing on some scrap, mainly concentrating on KTM-SV to see if I can get that to work with a brush. If it is an improvement on EM2000 it should be an excellent finish.

I'll be interested to see how the SV goes.
Heard good things about it a while back, If it had been available here.........

Jeff,

Thanks for the info, I'll give the paper towel/ soldering iron a go on the dent tomorrow. It's just outside the area of the scratch pad so a bit unlucky, I had a closer look at the scratch and it's more an elongated dent which doesn't seem to have raised the grain but I'll look tomorrow under magnification. A bit of a cow but there you go. I'm learning about some of the frustrations that you luthiers have to overcome. I'll order some blonde dewaxed shellac (or see if I can pick up some locally) not eh sort of thing that can be picked up from bunnies I guess. Speaking about Bunnies, I see in that other finishing post that you mention acrylic lacquer rattle cans at Bunnies, I might see if I can pick up a can and give one of my practice ply sheets a flash. Any idea what brand or which section of the paint dept. it is in?

Os

I too will be interested in your tests Mando. I've already ordered the KTM9 but just read Peter Brown's blog entries on the SV and maybe I was a bit hasty. Still, I gotta get this thing moving as I'm sure it'll get more dings if it's just sitting around while I procrastinate. As near as I can tell, now my finishing procedure will be epoxy back and sides - probably 2 coats, rub back with 400, 2 or 3 dewaxed blond shellac sealing coats and 3 days of 6 coats of KTM9 a day spaced about an hour apart, rubbed back each day and a light spray with spirit to improve burn in. Hopefully, that's about right.

White Knight crystal clear acrylic from the graffiti artist proof section.

Thakns Jeff,

I'll pick some up and give it a squirt!

Thanks for the dents/scratch removal advice Jeff, worked a treat. Dents were easy and came out higher than the surrounding area so were easy to knock out with a bit of 400. I ran along the scratches the same way which lifted them up to the surface and then sanded them back till the torn grain went. I reckon the scratches were up to about 1/4mm deep in places and they lifted up enough that not much more than a light sand got rid of 99%. Can just see a little bit of a mark but I'll live with that given that this morning when I had a good look at it I was convinced I would have to remove and replace the top plate!

I was reading your thread and thought I'd offer some of my own experiences with finishes. I don't care much for the water base lacquers, seem difficult to master the spray technique and it's about impossible to make an invisible repair in the future. I had a neck that was finished in it and had set about a year and still wasn't as hard as nitro. I'd recommend a go with the hard shellac, try spraying it using the method the fellow in the video is using to spray nitro. I scraped off the water based lacquer from the neck I mentioned and sprayed a couple of coats of shellac for sealer and it was smooth as glass using his spray technique. I kept the gun close to the surface and moving quickly, I'm using a hvlp gun and the overspray was minimal. I've used the hard shellac, it's a great product. I like the Timbermate pore filler, it's applied to raw wood, but you have to be carefull that you don't get it on the lighter wood as it will stain it, I brush on a coat of nitro lacquer on the lighter wood and it gets sanded off with the Timbermate. Spraying a coat of shellac over the Timbermate worked better for me than wiping it on, had some pull out wiping it on. Nice thing about shellac or nitro is that if it gets mucked up, it's not to difficult to start over and can be readily repaired in the future. Get lots of scraps and see what works best for you, good luck. Mike