How temperature affects set up

[Akira]

Ok, so this has been puzzling me for a while, and I know it probably seems like a really dumbass question, but...

How does temperature effect the set up of a guitar, especially floyd rose equipped guitars.

Heat causes metal to expand, so this would make the strings loosen, and lower action? But surely then the truss rod would also move due to the heat, and cause a rise in the action? I'm not sure how exactly it works.

For example, the sudden heat wave has caused the tuning on my guitar to go flat, but the action has rose, how does this work?

I know obviously different temperatures effect the set up of a guitar, I know that when the seasons change i'm gonna have to have my action, intonation, and truss rod checked, but what actually happens within the structure of the guitar to make these changes happen?

A really dumb question I know, I feel dumb for asking and there's probably a really simple explanation for it, but I want to know the method behind the madness.

:o

[Dr_simon]

I think the biggest deal is humidity which makes the wood expand. This will alter your action / intonation significantly .

[Akira]

I think the biggest deal is humidity which makes the wood expand. This will alter your action / intonation significantly .

Ahh, now that would make sense!

[aschleman]

To explain a little further what Doc is talking about...

Wood is a very porous material... When it's exposed to damp air (humidity) it absorbs the water in the air like a sponge... causing it to expand. When the water evaporates from the guitar it usually goes back to normal... However, if guitars are stored in humid environments for too long major things can happen... most of which are irreversible... Necks can become warped if the wood is saturated by enough humidity for a long enough period of time. Finishes can crack when the wood expands farther than the finish is capable of... In rare cases the wood can even split on certain grain types... If the wood for a solid body is cut a certain way that has hard grain lines next to softer grain lines... and they extend to the outside of the guitar... Sometimes you can get cracking where the softer grain expands and pushes the hard grain away... the hard grain may not expand at all since it is a denser part of the wood... When the water finally evaporates from the tiny pores in the soft grain it may crack where the soft grain meets the hard grain.

Humidity can also cause Necks, fingerboards, and bridges to come unglued... The glue can be not only affected by the humidity but also the sheer heat of an enironment. Think about it... how do you remove a bridge off of an acoustic guitar... you steam it until the glue is melted off... Also, with the wood expanding it helps to break the glue loose... I've actually had the neck on my Ovation 12 string come loose because my mom left it in her car one day when she went to the store... I went to pick it up and... flop... the neck and body were in two pieces. I simply had to reglue it... but it's s terrifying experience.

Some suggestions for storing your guitar... Get a dehumidifier if you store your guitars in a basement. Usually it's a good idea to have a dehumidifier running where you store your guitars if you live in a humid environment... Atleast run it during the summer months... Don't think that all humidity is bad... Humidity is good for your guitars. It keeps them from drying out. You just don't want to oversaturate the wood by exposing it to high levels of humidity and heat. It's a good idea to keep your acoustic guitars in their cases and keep a tiny humidifier inside with it... This will give the guitar a proper amount of humidity without exposing it to extra humidity outside the case...

Seasonal set-ups are common though... so don't think it's a sign of anything bad to come.

Just some extra information for anyone looking into this topic... Some general guitar awareness.

[Lordathestrings]

... For example, the sudden heat wave has caused the tuning on my guitar to go flat, but the action has rose, how does this work? ...

As you have pointed out, an increase in temperature will make metal expand. The strings will lengthen very slightly, which will reduce the tension on them, lowering the pitch of the note they produce.

The truss rod will also lengthen slightly, which relaxes some of the tension on it, allowing the neck to bow more than it was. This will raise the action and further reduce the tension on the strings.

Humidity changes will also have some effect. That will be less noticeable on a solid-body electric guitar, but could be significant to an acoustic. Humidity effects take several days to occur, but anyone who has left a guitar on a stand under the stage lights can tell you that thermal effects can occur in minutes. :eek: It isn't hard playing that keeps sending your axe out of tune - its the heat from the stage lights. That's why the tuning goes flat. Then, after you put your guitar away for the load-out, it goes sharp as it cools down and returns to normal.

[Dr_simon]

Living in iowa which is very hot and humid in the summer and very cold and dry in the winter, I sort my set up out twice a year / when I hear it needs it.

Normally I don't have to mess with the truss rod however the intonation usually needs sorting out !

[Akira]

Ahh thanks guys. :) It helps that I can now understand why it happens rather than just what happens.

I get my guitars set up usually in June and then again in November, which seems about right.

Thanks again. :)

[elklandercc]

How does the moisture get in with all the coats of paint and clear coat?

[Lordathestrings]

If it's polyurethane or somesuch plastic coating, the only access is through places where screws cut into the finish. In extreme cases, like splashing something on the guitar, this can lead to localised damage.

Older electric guitars, and almost all acoustics, are finished with nitro-cellulose, which breathes, allowing moisture exchange with the ambient air. It's a releatively slow process, kinda like osmosis. The danger is in sudden exposure to air that has a very different humidity level. The wood will give off, or take in, moisture rapidly in a thin outer layer, faster than the moisture deep in the wood can migrate to or from the surface. In extreme cases, this can be bad enough to destroy an acoustic or hollow-body guitar.