Science behind 2-3 coats per day

[VegasCustom]

Hey guys I just can't find a reason for only doing 2-3 coats per day of nitro lacquer. Spray can style.
What is the actual reason for not being able to do 5-7 coats per day? Would extending time between coats help add more coats per day? Just looking for a reason. No big deal.

 

[Gilmourisgod]

As I understand it, beyond a certain number, previous coats don’t have time to offgass sufficiently if you overcoat them too quickly, so they never really dry. That makes sense intuitively, but I don’t know of any “science” to back it up.

 

[LiptonJigglers]

I'm no expert and can only come to the conclusion that it ensures each coat has had time to dry properly before applying the next coat.

 

[VegasCustom]

Yea thats the only answer I can find and it doesn't work for me. If I can't find an answer ill sacrifice some wood and put this thing to the test. Its possible we're all just telling this to ourselves and everyone forgot the reason so someone has to push it.. at the very least to find the reason again lol

 

[chinjazz]

There’s a wealth of info buried here in valuable threads… Science for each practitioner can vary. Climate plays into it. Here’s a good thread: https://www.talkbass.com/threads/nitro-cell-lacquer-finish-schedule-tutorial.504392/

 

[Beej]

Here's Mohawk's official directions:

DIRECTIONS: Mohawk Clear Gloss Instrument Lacquer is a high quality nitrocellulose wood lacquer specially designed for musical instruments. Apply over E-Z Vinyl® Sealer, M610-800 or Mohawk WW Clear Lacquer Sanding Sealer (M610-2500), with standard or HVLP spray equipment.

Four to five coats of topcoat are recommended. Apply in light, even coats of no more than 3-4 wet mils. Scuff sand between coats with 320 grit stearated sandpaper. Total film build of the entire system, including topcoats, should not exceed 4 dry mils. Excessive build may lead to poor adhesion, cracking or cold check problems. May be applied at 1 hour intervals.

Allow to air dry 2-3 days then wet sand with P400A, P800A, P1000A, and P1200A waterproof sandpaper using Wool-Lube™ Rubbing Lubricant, M720-13xx, cut 1:1 with water. Classic Instrument Lacquer Page 2 of 2 Revised 6/28/12 formula versions: 1.009 Rub with Poly-Buf™ Rubbing Compound, M890-003. If reduction is necessary, use Lacquer Reducer 2255, M650-010.​

Sounds like applied and overall film thickness is more important than numbers of coats per day.

 

[T_Bone_TL]

One of the best finishes I produced in my youth was a school project that could only be worked on (at most) once a day, and none on weekends as it was in a locker in the shop. So it got one coat per day, at most.

 

[Pyrrho Epoche]

Yea, offgas. I put 6 coats of Verathane on my P bass and it took six months to offgas in my garage. Luckily, I had another bass to play.

 

[J Wilson]

You can certainly do what you want.

But I'd bet real money that 5-7 costs of a rattle can ( which is going spray more paint per press than a pro spray rig) is going to quite possibly check or swell up, and if it doesn't, it's going to take a long time to dry through: It's enough paint that the off-gassing from the first several coats is going to be almost trapped, lengthening your drying time by a lot. And ambient temp and particularly relative humidity can make things difficult. Improper sealing/priming can introduce problems.

Without a pro paint setup, it's just going to take as long as it takes. There's a reason that finished parts bodies or aftermarket repaints cost more than bare wood: It takes work to get a factory look paint job

But it's up to you.

 

[Beej]

And we've hit the front page. It was good while it lasted.

 

[J Wilson]

Not to mention if you THOUGHT it was dry, and then start to buff it . . . .

 

[micguy]

I am not an expert in finishing by any means, but one thing I do know (from unfortunate experience) is that rushing steps on a finish is the surest way to disastrous results.

Having learned that, when the directions say wait a day, I always wait 2.

 

[boxerrider]

Another vote for off-gassing. Besides the possibility of reduced adhesion, it can result in open pores or bubbles.

 

[Wesley R]

Here's Mohawk's official directions:

DIRECTIONS: Mohawk Clear Gloss Instrument Lacquer is a high quality nitrocellulose wood lacquer specially designed for musical instruments. Apply over E-Z Vinyl® Sealer, M610-800 or Mohawk WW Clear Lacquer Sanding Sealer (M610-2500), with standard or HVLP spray equipment.

Four to five coats of topcoat are recommended. Apply in light, even coats of no more than 3-4 wet mils. Scuff sand between coats with 320 grit stearated sandpaper. Total film build of the entire system, including topcoats, should not exceed 4 dry mils. Excessive build may lead to poor adhesion, cracking or cold check problems. May be applied at 1 hour intervals.

Allow to air dry 2-3 days then wet sand with P400A, P800A, P1000A, and P1200A waterproof sandpaper using Wool-Lube™ Rubbing Lubricant, M720-13xx, cut 1:1 with water. Classic Instrument Lacquer Page 2 of 2 Revised 6/28/12 formula versions: 1.009 Rub with Poly-Buf™ Rubbing Compound, M890-003. If reduction is necessary, use Lacquer Reducer 2255, M650-010.​

Sounds like applied and overall film thickness is more important than numbers of coats per day.

Sounds like a boat load of effort.y assumption is it is a lot of love.

 

[Jazzdogg]

My experience with nitrocellulose lacquer has been applying with an HVLP spray gun, as opposed to rattle cans.

As long as I haven't tried to shoot lacquer under high humidity, I've been able to apply way more than 3 coats per day - I've typically been able to shoot subsequent coats after waiting only about an hour.

That said, I ALWAYS shoot a test piece along the the actual piece being finished; I only shoot an additional coat on the project if the condition if the test piece justifies it. If the test piece is slow to dry, or the previous coat blushes on the test piece, I won't shoot another coat until the problem(s) with the test piece have been resolved.

Make sure you are very careful wearing a respirator and avoiding anything that can ignite the lacquer! It's very flammable, and the fumes are not healthy! In my old spray booth, the fans, light switches, etc. were all explosion-proof because the hazards are so real. Most of the commerical finishers I know have stopped spraying nitrocellulose lacquer in favor of water-borne products because business insurance and worker's compensation regulations, oversite, and cost are so significant.

 

[Grinderman]

It depends on the lacquer.

Mohawk makes the good stuff. I use their Finisher's Choice lacquer which is not limited to 2 to 3 coats in 24 hours, not even close. If the temperature is 70 degrees and the humidity is in the 50% to 30% range my re-coat interval can be every 60 minutes and be not even close to pushing my luck.

In the right conditions using Finisher's Choice, a body finish job applied correctly will easily be dry and hard enough to safely buff in a week, if you know what you're doing concerning buffing--even sooner if you're experienced and skilled enough.

What I DO NOT recommend using is Stewmac's ColorTone lacquer. It's overpriced crap that's positively inferior to Mohawk lacquer. Their chemical formation includes naphtha as part of the solvent. It takes longer to dry enough between re-coats, and much longer to dry and harden for buffing--more like 3 to 4 weeks... maybe 2 weeks at best if applied exceptionally thin and in the most ideal temp and humidity conditions.

For high-quality lacquer in formulated classic Fender and Gibson colors, I recommend Oxford Supply located in Windsor Ontario. They ship to the U.S., they ship out quickly, the prices are reasonable and they sell good stuff.

 

[VegasCustom]

Worth noting T Bird. Im just going to make a bunch of test pieces with various parameters and test it. This wont be scientific. Tons of stuff outside of control. But hopefully I find some reaons

My experience with nitrocellulose lacquer has been applying with an HVLP spray gun, as opposed to rattle cans.

As long as I haven't tried to shoot lacquer under high humidity, I've been able to apply way more than 3 coats per day - I've typically been able to shoot subsequent coats after waiting only about an hour.

That said, I ALWAYS shoot a test piece along the the actual piece being finished; I only shoot an additional coat on the project if the condition if the test piece justifies it. If the test piece is slow to dry, or the previous coat blushes on the test piece, I won't shoot another coat until the problem(s) with the test piece have been resolved.

Make sure you are very careful wearing a respirator and avoiding anything that can ignite the lacquer! It's very flammable, and the fumes are not healthy! In my old spray booth, the fans, light switches, etc. were all explosion-proof because the hazards are so real. Most of the commerical finishers I know have stopped spraying nitrocellulose lacquer in favor of water-borne products because business insurance and worker's compensation regulations, oversite, and cost are so significant.

Now safety I take extremely seriously. Im sealed in a hazmat suit and all electronics are explosion proof. I also have a series of 3 filters for the air to go through to protect my neighborhood and neighbors.
So far what I've noticed is extremely fast drying time and curing time. I tend to use aerosol cans, but I'm also so terrified of drips that most of my coats are probably not even considered a "full" coat. It took about 7 of my coats to cover the entirety of alder with white.

 

[VegasCustom]

It depends on the lacquer.

Mohawk makes the good stuff. I use their Finisher's Choice lacquer which is not limited to 2 to 3 coats in 24 hours, not even close. If the temperature is 70 degrees and the humidity is in the 50% to 30% range my re-coat interval can be every 60 minutes and be not even close to pushing my luck.

In the right conditions using Finisher's Choice, a body finish job applied correctly will easily be dry and hard enough to safely buff in a week, if you know what you're doing concerning buffing--even sooner if you're experienced and skilled enough.

What I DO NOT recommend using is Stewmac's ColorTone lacquer. It's overpriced crap that's positively inferior to Mohawk lacquer. Their chemical formation includes naphtha as part of the solvent. It takes longer to dry enough between re-coats, and much longer to dry and harden for buffing--more like 3 to 4 weeks... maybe 2 weeks at best if applied exceptionally thin and in the most ideal temp and humidity conditions.

For high-quality lacquer in formulated classic Fender and Gibson colors, I recommend Oxford Supply located in Windsor Ontario. They ship to the U.S., they ship out quickly, the prices are reasonable and they sell good stuff.

I am currently spraying Oxford for the first time. Better colors by miles. Better sprays. So far much better drying times. Also, its one of those companies with unbelievably good customer service. Could not agree more with you on that paint man. The Candy Apple Red is blowing my mind right now