Official Luthiers Forum!

Hello from Dundee, Scotland.
First post/first build.
Started my first build last year before I fully appreciated the problems humidity can cause.
As a result my first soundboard, which was basically finished, warped badly as humidity levels changed.
Also discovered that CA glue stains spruce yellow if not sealed first.
Anyway,the build was on hold for a while following this setback and in the meantime I have found myself getting into the Ukulele, so my first build is now going to be an all mahogany Tenor Ukulele.
Humidity here at the moment is about 70% which I now realise is too high for any kind of assembly but can I do anything meantime while waiting for levels to drop to the 40%-45% that seems to be recommended?
For instance can I do any or all of the following without suffering problems later:
1. Joint, thickness and cut to profile top/bottom plates including soundhole and rosette.
2. Thickness sides.
3. Bend sides.
4. Make neck blank (scarf joint /stacked heel)
5. Prepare top/bottom blocks.
6. Anything else?
Look forward to hearing from the experts.
Cheers

First of all, welcome to the Forum.
Not trying to be funny, but to be honest the best thing you could do is probably to control the humidity where you are building if that is possible.
I'm just up the road from you, and humidity is up and down like the proverbial.....

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I need info on this, too. I live in a small flat and have to work in the garage.
Had the hygrometer down there for a year... Min. 27% / Max. 90%.

I'd love to know how to work around it.

You can't work around that when dealing with things as thin as guitar plates.....you need to control the RH.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

I work in a basement where rh floats between 30 and 70%, most of the times sets around 55-60% which is high!!

1-I store my woods on an high shelf where rh tends to be lower than near the floor, take down workpiece for work/gluing ecc and than bring up again

2-when rh is high, no plate jointing, no brace gluing, no box closing, no binding, no gluing fretboard to neck or body

3-when guitar is ready, use a case humidifier

Greetings from Italy!

Andrea

You can:

Thickness all wood, bend sides, make bars, join plates, make rosette, make Neck, make bridge.

Which dehumidifiers are people using? I am considering buying an air conditioner with a dehumidifier so that I can hit two birds with one stone. The only downside to this is I will have to drill a large hole in my spare room wall.

When using a dehumidifier, will it be able to fight against the high humidity that will enter upon opening the door (to outside) that will be needed to keep cool in the room?

Thanks, Brian, I missed your reply. There's no way I can control the humidity down there. I did all gluing operations at about the right humidity but I wonder how effective that can be. How long at a certain humidity is long enough? Does this mean I can't build guitars in my garage? I've got nowhere else to do it. Gutting. I need to learn more about this.

Do all luthiers in the UK build in indoor dehumidified workshops? I've barely got electricity down there.

just a suggestion. Is it not possible to build an area framed in say 2 x 2 timber lined with thick plastic, assembly bench inside and a domestic dehumidifier inside? It will give you somewhere to use 24/7.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I wish it were possible, Colin! When the car is in there, I have to sit on the bonnet to work at my bench!

Maybe I'll try to borrow a dehumidifier from a mate who has one and do some tests in there. If I can put a double glazed window and a tight seal around the door, maybe that's a start. I need to work out how long would I have to run it for to achieve 45% and how long does the wood need to be at 45% before and after gluing operations.

OK. That tight!

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Aye, very tight when the car is in there, which it isn't when I'm working, but still. Makes it difficult to build me a box to work in!

I'd love to hear from anyone who successfully builds in a garage without a dehumidifier... What did the the great classical builders of Spain do before modern climate control?

here in the UK Nick our outdoor relative humidity is lowest in the warmer months http://www.bbc.co.uk/weather/2643743

still not down to 40% though

I am just a beginner so I don't know much... but I do know when the heating is on in our houses in the cold months, RH can become low

would it work to store wood in the house during this time, store freshly glued pieces there too or have a dehumidifier in the house?

I don't know, just an idea

Thanks, Mark! During the snow in the winter was when I noticed particularly low humidity levels in the garage.

Working indoors and out would present a bit of a challenge as I have three flights of stairs between the flat and the garage. It's bad enough having to carry up a bag of bits and pieces and whatever I'm working on. Maybe I could have a go-bar deck up here for gluing operations but I really wish I could keep it all to the garage. Hmmm *thinking hat on*

They worked around the weather, doing the operations that needed to be done in low RH when the natural RH was low. That's what I've been doing, and it works OK, but you need to have 5 or 6 underway or there's a lot of time when you can't do anything.

Others have made small drying boxes to store materials during construction.

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A man hears what he wants to hear, and disreguards the rest. Paul Simon

I'll have to try to find out how they use their dry boxes. I still can't quite imagine how long it takes for a top or back to take on, or lose, moisture? Could I keep the body wood in a dry box overnight, take it out and glue it up, and then put it back in the drybox? I suppose I wouldn't be able to leave glue to dry overnight? These aren't necessarily questions for you, Rodger,many thanks for our advice so far!

Maybe someone in the UK who builds like Rodger could chime in?

Maybe an enclosed gobar deck / trolley with a dehumidifier under it and a perspex door?

Also, I've read at least one luthier say that 45-50% RH was/is used in the States because it's deemed a safe, rough average for different regions. If the "rough average" across the UK was 10 or 20% higher, would that mean we should adjust this figure.... I guess most guitars are built at 50ish and live here pretty comfortably. And when, rarely, it does drop down into the 20s, I suppose the result won't be pretty.

This is doing my nut in! I'm so envious of all the Americans on here with big basements!!! Why do we build shoeboxes in this country?! Argh.

Thanks, Filippo!

May I ask how long the wood needs to be in that RH environment before you glue?

For instance, if I thicknessed the top and prepared the braces in the garage at 70%, how long would it need to be in the circa 40% environment before I could go ahead with gluing? If I had a go bar deck in a perspex cabinet with a dehumidifier below it, how long would I have to allow for it to acclimatise?

Sorry if I'm being a pain!

You should prepare the braces at the RH at which you plan to glue up (45% or whatever). I would bring my shop to the desired RH, wait a few weeks, prepare braces, glue up, and close the box while maintaining the desired RH at all times. I have had brace stock go banana on me from these amounts of humidity changes (70% to 45%).

Well, this is not good. I don't want to have to give up such an amazing hobby because of this.

I would give a top at least a day to acclimate if left in the open, but I wouldn't be surprised if it only took half a day. I would feel best if I gave it a week. I would want to give a rosewood back at least a couple days.

I've heard of people doing weight testing for moisture, but have not tried it myself.

I would not feel comfortable taking wood from a climate controlled environment and bringing it to a non controlled place for glue up.

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Pat

It is my semi-educated guess that tops, backs, and sides would acclimate in a matter of hours to a change of 30%. Braces would take a little longer, depending on their thickness. The good news is you don't have to wait that long for wood to acclimate. The bad news is you don't have much time to glue everything up and get it back in the dry box.

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A man hears what he wants to hear, and disreguards the rest. Paul Simon

+1!

As an amateur builder I really wouldn't worry so much. The humidity question is really important in the US where they have huge humidity swings and central heating which works. For UK conditions, building without humidity control is fine provided (a) you don't close up the body in high humidity, and (b) the instrument isn't kept next to a radiator, or equivalent.

I build ukuleles which are notorious for cracking in the US. Only one of mine cracked, and that one was forced to live in an attic for a year. I also own a 1920s Kumalae, sold to me from Scotland, which has no cracks - not sure if there's an uncracked example in the whole of the US.

I have a simple device made from two six inch by 1/4 strips of veneer, glued together with the grain at 90 degrees. It curls left if it's humid, right if it's dry. Straight is around 55%, and I'll close the box anywhere there or drier.

If selling your builds you'd want to be fussier, to avoid repairs and keep your reputation. But as an amateur, just tell the recipient how to look after it!

Pat,
Thanks for the suggestions, I'm happy acclimatising a room for a week and gluing indoors. That's not too bad.

Rodger,
Confirms what Pat is saying! I'll make sure to glue up in the same conditions.

Chris,
Cheers, Some great information! I'll breath a little easier having read that. I'll do what I can and implore anyone who has one (only me, my dad, and, soon, my brother! lol) to look after it carefully.


I was really starting to panic about humidity issues but even if I just have to run a dehumidifier in one room for a week or so before gluing up, it's not too bad.


Best to all,
Nick