Humidity... or the lack thereof...

[J.F. Custom]

Hi all,

Opinions please. I'm wondering what the Victorian luthiers do about the humidity or lack of?

In Brisbane, we were often around 50-60% humidity so you didn't have to wait too long to get a good day for critical jobs. But it could get up to 80% and stay there for weeks. After some time using the "wait for the right day method", I invested in a Delonghi Air Conditioner/De-humidifier. This was born from the frustration that the "right" days were not coinciding with my opportunity and vice versa. So great, that helped a lot and meant I was able to build pretty much any time. Perfect. Then I moved...

Now in Victoria, I appear to have the opposite problem, making my De-humidifier redundant (Mind you, the Air-Con part came in handy for the 45ËšC heat waves I seemed to have timed my entrance nicely for... ) My workshop here is still being completed/refurbished so I haven't had any problems yet, but it's just about finished and I am bursting to get in there and build. To my increasingly long-winded point, the few times I've checked the gauge, humidity has been about 20-30%. Does anyone bolster their humidity levels with a basic style humidifier as you can buy at the chemist? I'm adverse (financially) to install a fully electronic humidity climate controller... Opinions or suggestions or what do you do?

Jeremy.

[kiwigeo]

Im in the Adelaide Hills where outside humidity can vary markedly through the seasons. That said my workshop is well sealed and insulated and I manage to keep the humidity in the 30-40% range with a dehumidifier running and during the winter a small low wattage heater assisting.

[Allen]

When living in Canada, in the winter months is very common to have a kettle of water on the air tight stove use to heat many homes. Just to bring the humidity levels up to a more comfortable point. That may help.

I've also seen mention that in some drier parts of the world, builders will toss a bucket of water on the floor to bring up the humidity. Obviously concrete floors would be best.

What does an evaporative cooler do to the humidity? May be an option.

[graham mcdonald]

What is worth checking is the cycle of humidity during the day. Here in Canberra it is often down in the 20-30% range by mid afternoon in summer, but in the mornings it is usually 60% or more. I usually aim to do all the critical gluing around 2pm and that seems to have worked fine for the 15 years or so I have been building in this climate.

We have a couple of evaporative coolers around, but I have never thought about them for raising humidity in the workshop. I did indulge myself with a cheap ($300) reverse cycle air conditioner from KMart a couple of years ago, and that is wonderful for those +30C days

cheers

graham

[Allen]

........... I did indulge myself with a cheap ($300) reverse cycle air conditioner from KMart a couple of years ago, and that is wonderful for those +30C days

cheers

graham

Oh, those hot sticky days over 30. It's on my wish list too, but I'm afraid the power bill would take a hell of a spike.

[vandenboom]

Melbourne humidity is generally pretty good for building.

I bought a DeLonghi dehumidifier during my first build because the pre-reading I had done had created this impression of how crucial humidity control was. I was almost paranoid about it and had the unit running constantly for months during my first build.

These days, I let it run for the few days before & during steps like joining plates & bracing top/back and closing the box. If humidity gets below 30%, I just wait. My shed is also fully insulated (used to be a son's bedroom!!) so this helps.
I don't tend to worry about it too much for neck work - perhaps I should.

I did a really dumb thing on my 3d guitar - nitro finish mid winter - I left it to cure in the lounge room because I thought the central heating would assist the curing process. Never realised how central heating lowers humidity so much. A crack formed in the back!!

In Feb of this year when Melb had day after day over 40C, I had a guitar curing. Every day, I left it in the coolest room in our house - an unused bathroom.

As Graham said, it can vary so much throughout the day. For spraying, I spray outside (HVLP) and wait for humidity to drop as the outside temp warms. Humidity can go from 60% to 45% in 2 hours.

Frank

[Bob Connor]

I do much the same as Graham. In Geelong it'll get up to 70% overnight and that'll drop during the day to around 40% mid afternoon.

You have to keep an eye on the RH and make decisions on when is appropriate to be glueing.

[sebastiaan56]

Ok Im missing something in all of this humidity talk,

My previous experience with paper taught me that it takes time to equilabrate a material to the ambient RH. Australian testing standards required a 24 hour period for equilibration before we could do strength tests on paper. Tests I did indicated 3-5 hours in the RH controlled environment was good for indicative strength but not entirely reliable. Tests I did on reels of paper showed that the outside 2-3mm equilibrated over week but the inside of the reel remained at the % moisture that the paper mill provided it at for years.

Now paper is not tonewood, but the assertion that the time of day will affect the % moisture of the timber being glued is difficult to for me accept. I think it must take longer for timber to equilibrate than that. Has anyone got equipment to accurately measure this change? I'll start an experiment on some timber to measure changes in dimension at various times of day (the crux of the matter) but can onyone accurately do moisture content?

I trust the advice and experience but it goes against my previous training.

[graham mcdonald]

Seb,

Never thought of it like that and you are undoubtedly right. On the other hand gluing braces and fingerboards when the humidity meter reads around 40% works and I know from bitter experience that gluing braces when the humidty reads 60% will lead to many rude words when the RH goes down. The climate here is basically dry and suitable for lutherie most of the time unless actually raining (which it is a bit at the moment)

As a backup to my $25 humidity meter our local utilities provider has a really good weather page on their website at
http://www.actewagl.com.au/weather/ and that is a good backup if I am unsure. I do wait a couple of days after rain before doing any critical gluing, even if the RH meter says it is OK.

It needs someone more cluey about equilibrium moisture levels to comment how quickly a spruce soundboard picks up and loses moisture, but a wet piece of spruce cut from a billet will get to an equilibrium moisture level in a couple of weeks in an Australian summer, losing weight and shrinking several mm across its width. I don't think I would want to use it immediately, but any extra weight (ie water) loss is a lot slower as the water in the cells gradually escapes.

I am just glad I live in a climate which is basically suitable. I have seen the efforts lots of our American friends have to go to to create an environment they can build in.

cheers

graham

[jeffhigh]

I approach this a bit differently to most in that I build with the wood drier than the ambient RH will produce, by heating the plates in front of a fan heater for a 5-10 minutes before glueing on braces.
I use flat braces for the top and this induces a little arch after glueup when the top wood returns to ambient.
This effect happens quite rapidly, cetainly within an hour. so the raction of the wood to RH changes is very quick for the thin timbers we use.

I do it this way because
- I dont have a climate controlled workshop
- It guards against the top going concave
- It provides some protection against cracking if the guitar is taken into a low RH environment.

[Allen]

I've heard of some builders doing it this way as well Jeff. I'm going to give this a try on something small, like a tenor uke on the next build. I think a little arching won't hurt, and a good little experiment.

Certainly for the rest of my building. The dehumidifier goes on a week before I'l going to be glueing on braces, and stays on until the box is closed at the very least.

As far as how fast a spruce soundboard takes up and looses moisture, I've got no scientific test. But I do observe them turning into potato chip shapes when I bring them out of the Dry Room, and plunk them down on the work bench within minutes. They return to the normal shape in about double the time when they are returned to the dry room.

[J.F. Custom]

Hi everyone and thanks for the replies.

It seems there are as many methods and opinions as there are luthiers on here! Not that that is anything unusual in this field...

One thing I do notice is that no-one seems to use a fully controlled environment which is interesting.

I personally don't like being at the beck and call of nature untempered and prefer to stabalize the conditions in the workshop to some extent - at least more so than outside. I think I'll wait for the workshop to be finished so I can ascertain where the levels in there hover day to day. It is only a small area that is well sealed and insulated so it is likely to be pretty good most of the time. I just hadn't had to consider how to bolster humidity before - Brisbane is rarely below 30-40%, so I wondered what others did in this respect. Looks as though it will not be a major issue anyhow.

BTW, evaporative coolers do apparently raise humidity, according to a quick google search.

Jeff - how long have you been building like this and how have the instruments held up in differing conditions? I have read of other luthiers doing this but hadn't tried it yet.

Thanks again for your insights.

Jeremy.

[jeffhigh]

My first instrument built this way is about 16 months old, holding up fine.
I think there are probably some who dry out the top and back when they are heating it to use hide glue too.
If your ambient is 30 to 40 I can't really see the point in building at higher RH and then having to humidify the instrument to keep it safe from cracking.

[J.F. Custom]

Hey Jeff,

Thanks for the reply.

But no, you misunderstand me. My ambient is not 30-40% RH. When I lived in Brisbane it often hovered around 50% and was rarely low - more often higher, hence the use of my air-con/dehumidifier.

Where I am now in Victoria, my measurements thus far (taken randomly and not in the workshop as it's incomplete) have shown much lower results at 20-30%. I was curious if anyone in Victoria had found it necessary to bolster from 20 to say 40% and how they achieve this. I'm aiming for between 40 - 50% but it looks as though inside the workshop when finished is likely to be fine or need very minor adjusting.

Sorry if I did not make myself clearer.

Cheers,

Jeremy.

[jeffhigh]

My Mistake, I meant to say 20-30 RH.

My personal approach would be to build dry (and by "build" I mean the critical stage of gluing braces to the top and back, and to a lesser extent, gluing top and back to sides) rather than humidifying the workshop.

Consider these scenarios-

Guitar built at 25%RH
Goes to a situation of 20-30 RH no change
Goes to a situation of 50% RH top rises a bit needs saddle lowered

Guitar built at 45% RH
Goes to a situation of 20-30 RH
Has to be kept humidified or
- top goes concave and possibly cracks
-back flattens and may crack
-string height drops and strings rattle.
-fret ends sprout as fingerboard shrinks.

So make your decisions on building climate based on where you anticipate your guitars ending up.

[J.F. Custom]

Hi Jeff and thanks again.

I guess it's a bit of going with what you are used to and what has worked for you in the past. Much like Graham said, I am comfortable at about 40-45% because of the results I've had at this level. Having not built at a much lower humidity, I'm not as confident in the possible results which is why I posed the question as to whether others felt it necessary to raise. I know not to build at a much higher level.

My thinking overall is that if you can possibly build in this middle range, your instrument is more likely to cope with a wider range of conditions. I'm never sure where or what conditions my instruments might face over there life.

In any case, thanks everyone.

Cheers,

Jeremy.