Does the 'primer' need to be nitro?

[PoopSoupGuitars]

So i have a new build I'm working on and starting to think ahead to my most dreaded part: painting.

I'm thinking I want a Surf Green with a gloss clearcoat, and will go with a nitrocellulose on these. I have a can of general purpose primer (think it's acrylic lacquer) from a hardware store. Is there any harm in mixing solvents in that way? Nitro isn't easy to find where I am, so it means ordering online from the UK or EU and gets pretty pricey, so if I can save 30 euro on primer I will.

Thanks

 

[Uncle Daddy]

I've use acrylic primer loads of times, usually a filler/primer so I can flatten out any final imperfections. You can usually go nitro over acrylic, but not the other way round.

I normally use shellac as a first coat- button polish is fine, and it soaks up nicely on the end grain, ready to be smoothed off.

 

[Boreas]

Plain old shellac works well too, but may darken wood a little.

 

[schmee]

I have been successful with nitro over non nitro stains. But the stains are good and dry. Nitro as a base coat is fine. Nitro over something else COULD be a problem, but won't always. The Lacquer solvent will melt/bubble some finishes. (Lacquer thinner melts stuff pretty well) But often a lacquer coat flashes so fast there is no time for it to degrade the undercoat, however a thicker coat that dries slower could.

 

[Peegoo]

No, but it must be compatible with nitro, e.g., no puckering, wrinkling, etc.

Always (ALWAYS) do a test piece on scrap wood to make sure your finish plan will work.

Finding out otherwise, when applying finish to the guitar, is one of those feelings you'll remember for a very long time.

 

[eallen]

Acrylic lacquer and nitro lacquers are generally compatible in that they use the same solvent.

 

[PoopSoupGuitars]

Thanks all.

When you guys talk about shellac as an undercoat, you mean flakes mixed with alcohol applied as an oil, or the likes of Zinsser Shellac aerosol?

 

[Freeman Keller]

Poop, I'll tell you what I think as a general answer to your first question. By the time I'm ready to finish a guitar I've got a couple hundred hours into it and this is not the time to experiment or to ask advice on some internet forum. Your lacquer top coats MIGHT work on whatever primer you've chosen but I know that if I spend a little more money and get the stuff the manufacturer recommends I've got a much better chance. And as we have said over and over and over, test everything on scraps of your own wood.

Shellac is pretty much the 'works with everything' seal coat, and I have used it with good success, but if I have a choice between shellac and the manufacturers sealer I use the latter. I use shellac all by itself as a finish on vintage and classical guitars, in which case I mix it from flakes and apply it in the French polish technique. I've use Zinssner in a can and it has been fine, have never used the aerosol. I tried spraying my home mixed flakes in everclear and really didn't like it - it seemed to dry almost before it hit the wood. Brushing would be my choice.

Note that in the SM finishing schedule (which I follow) they recommend even just thinned lacquer as the washcoat and sealer

Nitrocellulose Finishing Schedule - StewMac

A step-by-step flow chart of nitrocellulose finishing.

www.stewmac.com

 

[PoopSoupGuitars]

Poop, I'll tell you what I think as a general answer to your first question. By the time I'm ready to finish a guitar I've got a couple hundred hours into it and this is not the time to experiment or to ask advice on some internet forum. Your lacquer top coats MIGHT work on whatever primer you've chosen but I know that if I spend a little more money and get the stuff the manufacturer recommends I've got a much better chance. And as we have said over and over and over, test everything on scraps of your own wood.

Shellac is pretty much the 'works with everything' seal coat, and I have used it with good success, but if I have a choice between shellac and the manufacturers sealer I use the latter. I use shellac all by itself as a finish on vintage and classical guitars, in which case I mix it from flakes and apply it in the French polish technique. I've use Zinssner in a can and it has been fine, have never used the aerosol. I tried spraying my home mixed flakes in everclear and really didn't like it - it seemed to dry almost before it hit the wood. Brushing would be my choice.

Note that in the SM finishing schedule (which I follow) they recommend even just thinned lacquer as the washcoat and sealer

Nitrocellulose Finishing Schedule - StewMac

A step-by-step flow chart of nitrocellulose finishing.

www.stewmac.com

Thanks Freeman. I am working on 2 or 3 guitars right now and this one is my own custom shape & really is more of a proof of concept so I'm less concerned about perfection (it's probably going to be a relic job) but you're advice is of course correct regarding doing things the right way. I hadn't seen that SM flow chart before, it's very helpful. Interesting that they recommend a seal, then grain fill, then seal again. I would have gone straight from sanding to grain filling (if not staining). Is there a logic behind the extra step?

 

[Freeman Keller]

For a long time SM recommended a paste grain filler (which they happened to sell). I used it on my early guitars and it was fine but you probably know that I now use finishing resin, which pretty much acts as its own sealer. The dilemma that I always have is when I'm going to stain and then pore fill, the resin seems to do good job of sealing the stain. I think their paste product was prone to bleeding.

 

[Ronkirn]

No there are some excellent synthetic primer/fillers out there that work quite well with nitro.... but you should try a professional painters supply.... the guy at your local hardware/paint store probably hasn't ever painted anything any more challenging than some old lawn furniture, and with latex at that...

and to add to Freeman's excellent suggestion... before you squirt ANYTHING on your project know what to expect... that means you have already finished some test piece to get the feel for what's gonna happen... Never, ever use a new product on the finished piece without testing and knowing first.... I t'll keep you from mumbling words your Momma was hoping you would never learn

 

[PoopSoupGuitars]

Thanks @Ronkirn. I took Freemans advice and went with a white nitro primer. Just did my colour coat today:

 

[Sea Devil]

It looks good so far! I'd be wary of those sharp edges when using any kind of abrasive, though. That includes buffing and polishing compounds.

 

[PoopSoupGuitars]

It looks good so far! I'd be wary of those sharp edges when using any kind of abrasive, though. That includes buffing and polishing compounds.

Good advice. Although I'm trying Nitorlack's 'relic' clear coat so scuffed corners might be ok in this case!

 

[Stratellafella]

Shellac is it ! all my builds get it I use it as a working primer under nitro seals great dries super fast I had to get a case from my bro cause they just outlawed it in states like NY you dont have to mix the flakes with alcohol unless your after a certain shade and I only know of one brand in aerosol Zinnsser bulleseye be careful the smell attracts flying insects of all kinds think it makes em wanna mate its an organic product Great stuff

 

[PoopSoupGuitars]

Shellac is it ! all my builds get it I use it as a working primer under nitro seals great dries super fast I had to get a case from my bro cause they just outlawed it in states like NY you dont have to mix the flakes with alcohol unless your after a certain shade and I only know of one brand in aerosol Zinnsser bulleseye be careful the smell attracts flying insects of all kinds think it makes em wanna mate its an organic product Great stuff

why would states outlaw shellac?

 

[PoopSoupGuitars]

Good advice. Although I'm trying Nitorlack's 'relic' clear coat so scuffed corners might be ok in this case!

Soooo.... its lookeding like Nitorlack's relic gloss works a little too well. The ffinish has already started checking. I'm fine with checking (thats why I bought it) but it's not supposed to happen until after you put in the body in the freezer or whatever.

Now I'm worried about wet sanding, polishing etc with these cracks in the clear coat. I did a few coats of shellac based sanding sealer under the primer so I think I should be good from water seeping into the wood, but what do others think? Can I still wetsand and polish an already checked finish?

 

[PoopSoupGuitars]

Should I try a couple more coats of clear to 'melt' the checked finish?

 

[Uncle Daddy]

Maybe use a non checking lacquer from the same supplier to slow down the cracking.
I used a checking lacquer from Dartfords, and let's say it needs some encouragement to crack.