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#1
02-20-2021, 10:36 AM
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Ripples In Finish
I have noticed that most, if not all guitars have ripples in the finish that follows the grain of the top. This seems quite obvious, but after finishing guitars for many years I have wondered why exactly these ripples appear. In a newly lacquered top there are no ripples, they take about a month to appear. I wonder why they appear. I have my theories but am interested in others.
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#2
02-20-2021, 11:10 AM
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I first thought about this as I was touching up my HD-28 and the touchup was obvious only due to the lack of ripples in the newly lacquer area. After level sanding the finish is of course level. So why do ripples appear? 2 things may explain this. The spruce does not end up completely level after being sanded due to the rings having different areas of density leaving ripples in the unfinished wood. After finish is applied and level sanded the finish is perfectly flat but because the lacquer has different thicknesses between the rings, as time goes by it shrinks then leaving the ripples of the wood exposed.
The other option is that the wood is actually flat after being sanded and the finish is level after being sanded. The ripples appear with time as the wood expands and contacts with temperature and humidity changes.
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#3
02-20-2021, 11:59 AM
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Quote:
__________________
"What have I learned but the proper use for several tools" -Gary Snyder Bourgeois DR-A / Bowerman "Working Man's" OM / Martin Custom D-18 (adi & flame) / Martin OM-21 / Northwood M70 MJ / 1970s Sigma DR-7 / Eastman E6D / Flatiron Signature A5 / Silverangel Econo A (Call me Dan)
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#4
02-20-2021, 12:04 PM
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Quote:
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#5
02-20-2021, 01:50 PM
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Lacquer never fully cures and evaporates very slowly over decades.
Evaporation, curing, settling and thinner finish with decades of age show ripples as it settles into the grain.
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#6
02-20-2021, 02:08 PM
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Quote:
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#7
02-20-2021, 04:39 PM
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Not necessarily. The Winter and Summer growth (darker and lighter lines) take up and and release moisture at different rates, among other things.
The less dense summer growth will also tend to contract more than the denser winter growth and that can create the unevenness.
__________________
"What have I learned but the proper use for several tools" -Gary Snyder Bourgeois DR-A / Bowerman "Working Man's" OM / Martin Custom D-18 (adi & flame) / Martin OM-21 / Northwood M70 MJ / 1970s Sigma DR-7 / Eastman E6D / Flatiron Signature A5 / Silverangel Econo A (Call me Dan)
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#8
02-20-2021, 05:17 PM
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You can surface a top very close to dead level, apply finish, and have ripples show up anywhere from a few months to a few years later. It's simply a matter of the long term shrinkage of the wood varying between summer and winter growth. The more perfectly quartered the top is the more apparent this will be.
It's not always a problem, and when it does show up it simply highlights that the wood does indeed change over time. The surface finish usually telegraphs the change as it conforms to the surface of the wood. Thick UV cured polyester finishes often don't show this, and that should tell you something about what it does to the ability of a guitar to produce good tone.
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#9
02-20-2021, 07:59 PM
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I hadn’t thought about it until you mentioned it, it it occurs to me that I only (mostly) notice this on tops with a thin lacquer finish rather than something like a thick poly finish, so I therefore see ripples as a good thing - like bear claw...
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#10
02-21-2021, 10:19 AM
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Great replies, I like having discussions like this about even the most trivial topics
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#11
02-21-2021, 12:49 PM
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It happens with all finishes unless they are applied at differing thicknesses. A thick finish will not show the ripples as willingly. There is a vast difference in thickness between a 3 to 5 mil finish than compared to an 8-10 mil finish --- massive, massive difference in how tough the finish will be. Nevertheless, I still believe a lot of these thicker finishes do have some degree of "rippling" over time as well. Additionally, it is also very easy to have a thick nitro finish as well. By thick, I mean close or above 10mils. However, with nitro it is much harder to get super thick finishes - the modern finish materials will allow you to build the film much faster if that is your goal.
For luthiers, staying under 5 mils should be the goal and that can be done with just about any finish. Getting thinner than 5 mils is challenging. Getting a 2 to 3 mil finish is substantially harder than getting a 5 mil finish but it is definitely worth it in terms of tone. None of the big manufacturers are going to be giving you 2 or 3 mil finishes. I use a urethane finish on my guitars that is around 2 to 3 mils on the top - that is the thickness of Scotch tape, BTW. As you stated earlier, it is the movement of the grain that causes the very slight distortion in the film. Last edited by Simon Fay; 02-21-2021 at 12:54 PM.
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