Lacquer Curing/Drying Before Final Polishing

[klooker]

Wait. The longer the better. You don't want your soundboard looking like a washboard!

Now there's some motivation to wait.

It's funny you said that because during the lacquering, the soundboard had ridges in it like a washboard. After 3 coats, I flattended it down, & put on 3 more coats.

Would this washboard effect be a result of not enough sealer or is it just the nature of finishing a soft wood?

Thanks,
Kevin Looker

[kencierp]

Hi Kevin,

Not to undermind any of the well meaning advice here -- I just want you to know that I have been using Deft for about 40 years now. I have applied it to furniture and art objects we sold commercially wholesale and at art show during that same time period. Not to mention Guitars, wood banjos, dulcimers and other musical instruments. I never waited more than 10 days for final level and polish and never had a complaint and for sure never had a finish that looked like a washboard. Waiting is good -- however, if not using a power buffer polishing a few day early will not get you into trouble with Deft. I doubt if there is one professional instrument builder that did not bend the (curing) time curve to get out a commisioned project on time. Note: I am hopeless an engineer, when a coating data sheet states the coating's chemical action ends and it is completely cured after X number of days or hours I believe it. Works for me.

As for the ridges in the sound board -- that is a whole different issue -- that is caused by sanding too aggressively with the low grit papers. What has happened is soft grain has been removed faster then the harder grain. Sanding with the grain using a sanding block will still remove the soft grain faster. The practice of wetting the spruce before sanding can make this situation even worse. Believe it or not Frank Ford (frets.com) recommends sanding across the grain (personally I don't sand cross grain ) using the same course to fine progression. I have found the best way to prevent the "washboard" condition is to use a random orbit sander for more course grits followed by block sanding 220g and 320g.

[tippie53]

I do sand across the grain and I only wet the spruce once to raise the feathers of the grain. The thing that many may find confusing is that lacquering is as much technique and application. Also , it isn't what you put on as much as it is what you let on . As ken points out too much sanding can be worse than not enough. You can really make this thing look corodroyed if you are not careful. Also I do not sand beyond 220 grit .
I did stop using deft and went with the instrument lacquers and I found that I did have a better result , but I did use Deft in my early days . I am not disagreeing with Ken , it is I just went with another product . I also use vinyl sealer and stopped using shellac .
So you do have to find what works for you. Ken and I may use different techniques and product , but in the end it is the final result that we are looking for .
I find that you want a green build of finish to about .016 to .020 . After curing you can see this shrink as much as .005 to .008 . Lacquer is amazing stuff. I do use byutle acetate as a retarder and thinner to help flow out and get a smoother build with less orange peel.
One big thing is that you must be aware of the safety issues involved with this stuff. It is explosive and can cause health issues so wear a real finish mask not the paper ones and be sure you have no open flame or sparking . It is worth the effort .
My finish schedule is spray a coat every hour for 8 hours . I measure build by placing a business card at the soundhole . After 8 coats you should see the .016 to .020. With spray cans it may take more coats. I let this set 3 weeks and level sand starting with 320 and working through the surface ripples. Once I bottom out I am at 800 and I am wet sanding so that I get as level a surface as possible. I then hit 3 light and thinned coats , let cure 2 weeks and start off with 600 wet working to 2500 wet then buff and polish . . I would like to see Ken post his schedule so you can see , that it may be different but we both found what works for us.
There is more than 1 way to skin your knee to.

[John S]

Is this true for waterborne lacquer as well?