Letting Lacquer Cure...Do I Really Have to Wait??

[Pete Andreev]

Hey guys I know this is a question with no definitive answer. I've heard 10-14 days, then I've also heard some say that a week should suffice. I've also heard there are some variables that can affect the time...hot summer days can speed up the process apparently?

It's been almost exactly a week since my last coat. I refinished the neck on my 335. I'm wondering if it's alright to go ahead with the sanding, buff, and polish process...what do you guys think? What exactly happens if you start the final finishing process too early?

[Mike Kolb]

My own experience has been.... the longer you wait, the better it turns-out!  Yup, the temp & humidity plays into the time period, but I don't trust my judgement, so I let the calendar do the determining. 

Sure, there's a definite temptation to "get on with it" and move the project along, but it really does pay to just put it up somewhere out of sight and go do something else.  I've rushed lacquer-curing with decent results and some not-so-decent results. 

These days, using two weeks as a cure-time seems to be about right, but if I can afford to wait three weeks, so much the better.  Mentioning this to repair customers in advance serves to forestall a lot of "is it done yet?" calls. 

[Frank Ford]

Lacquer is an evaporative finish - it hardens as the solvent escapes, and in the process it shrinks considerably.  Rub it out too soon, and you'll see distinct shrinkage in the film so that pores and other surface imperfections will be prominent in reflected light.

The drying time is dependent on a number of factors - the volatility of a particular solvent, temperature, humidity, and most of all, the thickness of the lacquer itself.  Put it on too thickly, and you can be in for a long wait.  And, as you consider thickness of the film, don't forget that those little divots and pores are where the lacquer is the thickest, and they're what you'd like to avoid showing up later.

If you talk to the guys whose lacquer work has the best look, you're likely to hear they are strict about allowing full drying time before final block sanding and rubout.

I'm with you, Mike - when I take in lacquer work, I tell folks to be prepared for a four-week wait. . .

[Ned Knepp]

I have a guitar that I set aside a couple of months ago to cure. When I pulled it out last week I found that all of the filled spots have showed up again. It's astounding  just how much a finish can shrink. If you want to to look good you really have to wait, nothing else seems to work.

Time to find another project?

[Pete Andreev]

Good job guys...you've convinced me to do the right thing and wait. I think I applied a pretty thick nitro lacquer finish...it's the full length of the back of the neck and I used just over one can of aerosol lacquer.

Is there any way to sort of test to see if the lacquer is cured enough? Just makes me curious...it's been right around an avg high of 80 degrees over the past 4-5 days and I'm wondering how much this may have affected things.

[Peter Poyser]

Quote: "I think I applied a pretty thick nitro lacquer finish...it's the full length of the back of the neck and I used just over one can of aerosol lacquer."

 

 

Pete, Think Thin.

For sure it goes against the grain of all out natural instincts.

We want to complete the job, and with a full Spray Gun in our Hand, we have the means to do just that.

But the truth is, Lots of Wafer Thin Coats, carefully applied and gradually built up, allow the  Solvents to most Efficiently Evaporate, in the Quickest Possible Time.

In the Final Finish, when all the Processes are Complete. Many of the Shrinkage Related Problems that can beset a Product are thereby avoided, and the Frustrations of Unhappy Consumers too.

You can finish the job faster, by applying a thick coat more quickly, but unless you have Proper Facilities to completely cure such a coat, and this is the real issue, all you have done is to extend and delay the point at which the Finish will be Finally Cured. So what appears to be Gain, is in reality, an Illusion.

 

 

This presents you with the second tantalising temptation.

Rubbing Down and Buffing a Finish whose Curing Process Cycle, is still Chemically Morphing, and is nowhere near being Completed any time soon.

Quite apart from not being able to deal effectively with surface problems that are still, yet in the process of emerging; the potential difficulties that could be encountered, involved by introducing friction and heat, to still curing material, is a danger, clearly best avoided altogether. Frank, (the Perry Como of Re-Finishers) has a Commendably  Easy, Relaxed Approach to this, that is Ideal for Achieving the Most Satisfying Results.

 

 

But.

All this is amusing to me, because in the Facilities I am used to, everything is the other way around.

We Cure with Heat, using Controlled Flash Off Areas, Fast Acting, Surface Curing Inter-Coat Ovens, Coupled to Convection Heat, (this is to surface harden for instance a Colour Coat, so that were Dirt or Contamination to Fall onto the Finish whilst Curing, the Particulate  cannot Sink Deep into the Finish), and thus can probably be Successfully Polished Out without Re-Finishing; before applying Clear Coat, after which Heat Curing Completes the Job.

Almost.. In fact, Continuing Curing of the already Very Hard Finish allows Fine Polishing Operations and if necessary, any Re-Work to take place. But within 72 Hours the Finish will be Rock Hard and Impossible to Work. Every Unit is "followed by computer tracking" and the Hours it takes to Complete the Processes Recorded, and if the Unit can't be Successfully Finished in the Allotted Time, the Unit is Scrap. It's why we have to Track the Hours.

Certain Types of Modern Chemicals and Processes used in Industry, demand extremely tightly controlled windows of specification, in every possible respect one could imagine.

 

 

Lots of Finish Problems appear to be Emerging on New Units, Fresh Out of Guitar Factories these Days.

Part of this is caused by issues due to the Introduction of New Technologies, New Incoming Materials connected to More Efficient Processes, including New Methods of Curing along with Lean and Mean Manufacturing Philosophies.

However, personally, I am convinced that in the Pursuit of Higher Unit Output Volume, (which probably Triggers Bonuses) that Short Cuts are sometimes taken in particular Instrument Plants, including Speeding Up Certain Processes, Reducing Curing Time, and "as a result, certain Manufacturers Products are Widely Reported by New Purchasers, as having strangely "Waxy", "Soft" and "Problematic" Finishes, as a Result, and impossible for the Consumer to even clean without problems whereas the Finish, should be Solidly Hard.

 

 

Frank's, Gentlemanly World, of an Occasional  Pass from a Spray Gun, Once every Week or Two, is a Class Act for Repair involving these Traditional Finishes, you should try to Emulate in Every Way Possible.

At times, dependent upon environmental conditions, you may even find a Drop of Retarder, to Extend Curing Time, Positively Advantageous.

The Results will Speak for Themselves.

 

 

P

[Hesh Breakstone]

Some great advice here!

Pete I let it cure for a month and put it out of sight and out of mind in a temp and RH stable place where the gassing off solvents do not present a health hazard to anyone or anything.

One way to tell if you have not waited long enough is when you buff through the lacquer and have to repair it..... but I would not recommend this method..:)  Point being it's way easier to burn through if we don't wait long enough...

When I was building I tried to accelerate the finishing process and only waited two weeks and found that my sand paper clogged up way faster, I burned though while buffing, and as such learned that as they say there will be no wine until it's time - so-to-speak...

Like Frank we tell folks a month too we also add that the reason why it's a month is that the lacquer has to cure so we are essentially waiting for paint to dry.  Folks seem to understand this analogy and thankfully also understand it's no one's fault that paint has to dry.

[Russell Vance]

I would like to reiterate and "plus 1" the advice here - excellent stuff and the advice to "think thin" from P2 along with the solid advice to "put em up the back and forget about them for a month" theory of hardening/gassing out/curing.    

FYI: I have attached a quick fuzzy phone pic of a new MIM Nashville Tele just across the bench that spent a month in our new ice age here down-under in Oz.  As P2 noted, the new modern "speed is money" approach to life coupled with a full 28 thou thickness of slab finish did not fare well.   I suspect we will see more of this.

Rusty.

[Mark Fogleman]

I just saw the Stones this past week.  Shattered 

[Frank Ford]

Rusty - thanks for posting that photo - it's just about the most dramatic finish lack-of-adhesion photo I've seen!

We do see those production "time-is-money-narrow-window-for-error" kinds of problems Peter mentioned, and entire runs of instruments have been scrapped because of finish adhesion issues.   I assume the group here is more into finish technology on the order of a hundred years old, and that's what we're generally discussing.

As a Martin warranty guy, I sometimes see "traditional" nitrocellulose lacquer finish separating from the "high tech" vinyl sealer that's been in use for the last couple of decades.  Curiously, it's a problem that simply does not exist if the sealer is good old natural shellac. Old Martin guitars NEVER have that issue.  Unfortunately, the use of shellac takes time and training, so it isn't quite compatible with the bean counters in the front office. 

[Russell Vance]

Hi  Frank,

That MIM separation image was more a FYI item for the general knowledge bank than a comment about modern finishes.   We have seen it before but just not that bad. It will however be a relatively easy finish strip. 

We are long time nitro finishers ourselves and intend to stay that way - there is much to like about the traditional finishes and not so much to like about the plastic.

Regards, and have a good 4th.

Rusty.

[Hesh Breakstone]

Looks like they dipped it.... wow.....

Have a little Tele with that finish...:)

[Paul Verticchio]

All that's missing from that pic is a bowl of Salsa for the chips ;)