Why Can't I Lay Poly Over Lacquer?...

[Southpa]

This guitar is still my experimental finishing project and I've learned a valuable lesson tonight. When you start with one type of paint then you better finish with that type of paint. Here you see a water based polyurethane clearcoat (called Varathane) sprayed on top of cured acrylic lacquer.

I'm not pissed or anything. I should be able to peel it all off in a few minutes and finish the job with some clear lacquer I have laying around. Consider it a valuable lesson that I'm happy to share with all those folks who are just wondering.

Edited March 27, 2006 by Southpa

[Maiden69]

darn bro.. you should had remember that we disscussed this a while ago.

http://projectguitar.ibforums.com/index.ph...topic=13412&hl=

I had the same problem an posted about it, sorry to see that happened. But you can peel everything and clean up with denaturated alcohol, then respray with laquer.

[AlGeeEater]

Ouch man, how did it start to come up, did it just wrinkle and peel up?

Oh and I wouldnt go applying a harder (poly) coat over a softer (acrylic lacquer) coat.

Oh well, you live and you learn

[Southpa]

We're all still learning. Like I said, I'm NOT po'ed at all over this. The bottom line for all polyurethane type paints is that a good scuffing is required before application. I used 800 grit which was obviously too fine and did not give the clearcoat a good enough base to stick properly. The main problem with this particular material is that its water based. So you can guess what will happen when you start wetsanding, . Minwax poly would have worked better because its oil based. I've used Minwax poly quite a lot and have had good results in the past. The only way to learn is to try out different materials and see what happens. Personally, I like to see things first hand.

[Venom300]

The main problem with this particular material is that its water based. So you can guess what will happen when you start wetsanding, . Minwax poly would have worked better because its oil based.

Hate to do it but im a newb... I can't guess what would happen but sure am curious. Is water based material easier or harder to wet sand than oil based material?

Steve

[1576]

The main problem with this particular material is that its water based. So you can guess what will happen when you start wetsanding, . Minwax poly would have worked better because its oil based.

Hate to do it but im a newb... I can't guess what would happen but sure am curious. Is water based material easier or harder to wet sand than oil based material?

Steve

Being water based, the implication was that as soon as you start to use water with the wet and dry paper for flatting lubrication, it will re-activate the lacquer and turn it all stodgy. In my (limited) experience of water-based finishes however, I always found that once the lacquer had cured, water didnt affect it in the least. After all you get water based paints and lacquer for external use. Ive always used solvent based lacquers for guitars, never oil based.

[orgmorg]

No, once the finish is cured, it is no longer affected by water. It is waterborne, technically, not water based. The water is used to distribute the solids which are suspended in it, but those solids are not actually water soluble.

[Southpa]

Here is another thing to watch out for when dealing with lacquer. Laying it down too heavily in some areas causes "crazing".

You can see how the clear lacquer worked on the charcoal burst paint before it had a chance to dry. It only occurred in a few spots but basically I'm looking at lots of sanding and repainting the entire guitar to get it looking right. And then being more careful with that clearcoat. I'm learning quite a bit off this guitar and I hope its getting passed along. On the plus side, if I ever wanted to do some relicing it looks like a good way to get that natural "checked" look found on many early nitro coated guitars.