Sanding Sealer

[Dave M]

In a continual effort to try to improve my nitro spraying technique (it's really not going that well) I went through Robbie O'Briens video course recently.

He suggests a fairly serious sander sealer coat before using the finishing clear coat. Indeed he seems to ladle it on with a spoon! He aims to have a pretty near perfect flat surface before moving on.

I note that G&G don't really talk about this in their section on finishing.

I wonder if there is any concensus on this among the people who are using nitro? Do you bother with this stage?

I am using (Indian) Rosewood for the first time and am hoping the sander sealer might help with the slight faults in pore fill that I have.

Dave

[Allen]

If you are going for a high gloss and perfect finish, then your pore filling / sealing has to be pretty much perfect before you proceed onto your top coats. Most people are far too impatient and jump ahead before getting this critical step done.

There are lots of methods to prep that timber. I've tried heaps of them and have settled on Bote Cote epoxy. Never any sink back which is very common with lots of other procucts and procedures.

Can't speak to Robbies method as I haven't tried the latest product he is using.

[blackalex1952]

I'm a nitro man! I have tried the sanding sealer from Durobond as I use their nitro. It seems too vinyly for my liking (there's a new word!)
I sometimes use either an epoxy fill or plaster of paris which sands off easily, along with a stain which matches to wood. I have also used shellac and hide glue so there are some options for you. The plaster, shellac with fine dust from a sander and hide glue are pretty inert, so less exposure to dangerous chemicals...yours-Nitro Man!

[Dave M]

Thanks Allen I have finally appreciated what you say about getting the surface right before you start,

And Ross I am also keen on nitro. More so lately when I had to remove a coat on the top of another guitar. It is seriously tough, which I think one wants on an instrument that is constantly handled and worn.

My specific question was whether people do tend to use a sander sealer. The one I am using is from pretty much the only supplier of instrument lacquer in the UK. It doesn't seem to be too vinyly once you have sanded it back.

But I guess since it contains quite a high level of solids (presumably vinyl resin) it might obscure the grain a little compared to a clear coat lacquer.

PS I discovered today that warming up the sander sealer/lacquer improved the spraying quality enormously. I have it stored in a fairly cool room so the already fairly high viscosity of he sander sealer was probably too high. (no I didn't actually measure it!) I shall warm up my clear coat stuff to see if it reduces the orange peel a little. Dave

[blackalex1952]

I have never had a problem with orange peeling. I have always warmed my thinned lacquer, in the paint pot, in tepid water prior to spraying. As long as the nitro can offgas effectively at ambient temperature. Too thick a coat and it case hardens but is still soft underneath, so drying times increase. I am thinking that may be the reason one guitar I sprayed last year has developed some crasing..ie, little cracks in the finish. It just occurred to me that spraying too heavily and respraying several times before a certain level of off gassing might cause a soft chewy centered then case hardened etc-layer upon layer? Just guessing there...Alan might know, and probably does, much more on this subject. I don't spray below 20C ambient temperature either. But a lot to be said re pre warming the lacquer mix and applying thin coats. Cheers, Ross

[Allen]

I use the 2K Polyurethane sanding sealer in the system I'm finishing with.

All finishes are speced to be sprayed at 20C to achieve the correct viscosity per their reducer / thinner recomondations. If it's still too thick for your liking then warming it up even more certainly will help with spraying thinner film and it's flow out.

When I was living and spraying full time in Canada I always had the cans of mixed paint, catalyst and solvent in a hot water bath just prior to filling the spray gun.

[Dave M]

Thanks guys. It is nice to know that warming the material is a pretty common thing. Although we are not too cold yet here in the UK the particular space I have the spraying gear in is pretty cool. I will continue with the warming regime.

Indeed it might be the one thing after playing with dilution with thinners, trying a bit of retarder etc that finally get's my spray coats to flow.

So thanks. Dave

[blackalex1952]

Go with the FLOW- :Ya just gotta FEEL it ,man! -Ross