Cracked/split top

[phavriluk]

I suspect that building in dryer (drier?) conditions would be conducive to avoiding cracks in the future. I wouldn't be humidifying a wintertime dry work area.

Some years ago I had a discussion with Dave Nichols on this very topic. He stopped building in the summer and waited for humidity to settle down during cooler weather. He absolutely did not humidify during heating season.

This reflexive genuflection to the sainted 45 percent can be overblown and it needs to be carefully considered, not just automatically pursued.

And all nine of my scratchbuilt guitars followed Dave's shop practice, no problems yet.

[MaineGeezer]

Consider the implications of building at 50% humidity. The guitar is never likely to be more than 25% from its build humidity. The humidity can drop to 25% or go up to 75% and the stress on the guitar is still at most the stress caused by a 25% humidity change. If the change can be made to happen "slowly," e.g. keep the guitar in a closed case for a week after moving it so the guitar can gradually adjust, I would guess the guitar would be fine.

So does anyone believe that?

[MaineGeezer]

Duplcate post

[tippie53]

I had been at daves shop many times, and he did in fact humidify , he use a lasko humidifier , they do a great job if you can hold at 42% your fine.

[phavriluk]

Consider the implications of building at 50% humidity. The guitar is never likely to be more than 25% from its build humidity. The humidity can drop to 25% or go up to 75% and the stress on the guitar is still at most the stress caused by a 25% humidity change. If the change can be made to happen "slowly," e.g. keep the guitar in a closed case for a week after moving it so the guitar can gradually adjust, I would guess the guitar would be fine.

So does anyone believe that?

I do, all day. At least in New England, and anyplace that has a real winter.

[MaineGeezer]

Here's another theory for consideration:
Wood that has been air dried for an extended period (years) is less likely to crack than wood that has been artificially hurried through the drying process (kiln dried, torrified).

Really old wood has characteristics to it imparted by age that a fresh new board doesn't.

What do you think?

[tippie53]

a hygrometer will be a help but be sure they can be calibrated. I have a few digitals that are junk so be sure you can calibrate. I also have analogs and be sure you see calibrated or certified. I have an abeon a labratory hygrometer and this is accurate and I compare the others to that.
If you can keep 40% your fine. Under 35% damage occurs

[JLT]

If you wanted to salvage the present board instead of buying a new top, here's some thing to think about:

1. The crack at the top (head) of the board is nothing to worry about, since your fretboard will cover it. A little reinforcement behind it would not be a bad thing.

2. I don't know if you saved any of the pieces you trimmed off the soundboard, but I've rescued soundboard cracks by reducing the scraps to powder by sanding, mixing in with your glue until you have a paste, and then filling the soundboard cracks with the paste. When the top is finished, you shouldn't be able to see the crack unless you really look. Again, a bit of scrap at the point of the crack would be a Good Thing. I use a diamond-shaped patch made of spruce with the grain running at ninety degrees to the soundboard's grain.

[jread]

Just chiming in that I had a top warp into a big half circle after joining and gluing a couple weeks ago. I tried to flatten it to brace but the seam popped like the one we are discussing. I just scrapped it and will use the spruce for the strips that go over the center seam in future builds.

Some pieces of wood just don’t want to be a guitar.

[MaineGeezer]

I had a back go from convex to concave. It's amazing what a little moisture will do.

Hygrometers, and the accuracy thereof: Everybody else probably already knows this, but I recently found that there are a gazillion videos on YouTube explaining how to calibrate a hygrometer using regular table salt to establish a reference point of 75% humidity. In brief, you put the hygrometer in a sealed container you can see through along wit a couple teaspoons of damp salt in a bottlecap or something similar, seal it up, let it sit for 24 hours, and the hygrometer should read around 75%. The damp salt (moist but not soaked) has an affinity for water that results, in a closed environment, of a humidity level of 75%. If the hygrometer reads something other than 75%, verify that the salt is still damp[ but not dry or saturated. If it's still nicely damp, adjust the hygrometer top 75% if possible. If not, remember to add or subtract the appropriate correction factor.