Official Luthiers Forum!

I know UV light is used for curing lacquer but I'm not up for building the set up required. However I did get round to wondering about sunlight. I'd stress that I live in Sussex in the UK. It's a beautiful spring day here, brilliant sunshine, about 60F - this isn't Arizona! You wouldn't worry about leaving your guitar in the sun on a day like today. Just wondered if it would speed the lacquer hardening. I'm using Behlen waterbourne.

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"There is hope in honest error .... ". Charles Rennie Mackintosh.
http://www.ianchisholm.co.uk

Don't know the answer but I love the photo

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Steve Smith
"Music is what feelings sound like"

Cool photo!
I don't know anything about water-based lacquer, but I would be concerned about sunlight changing the color of the wood.

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wah
Wah-wah-wah-wah
Wah

Maybe, but in my experience waterborne responds to two things. Warm weather and low humidity. (But I do like the picture!!!)

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Joe Beaver
Maker of Sawdust

That soundboard could get pretty hot if left too long in the sun, even in the UK. I once placed an unbraced soundboard out in the sun to tan it. It curled up alarmingly, presumably because the sun was drying out just one side of the soundboard. There's a certain risk to leaving it out in direct sunlight IMO.
A lot of freshly applied finishes will also react to direct sunlight and bubble as the solvents off gas.
If you want UV just place it outside on a sunny day but out of reach of direct sunlight. There's still plenty of UV flying around on Spring and Summer days. Just be careful of those sudden showers, we tend to get a lot of them.

I confess the photo was a gag. Out of direct sunlight is the way to go, warm weather and low humidity sound good. Also I regularly turned the instruments and the finish had already dried for a couple of days so hopefully was past the out gassing stage. What I find with Behlen waterborne is that it is effectively dry in a day but is still slightly milky. It then takes a very long time indeed to become truly hard and glassy clear - it does get there but you have to wait. What I observe on these guitars is that a couple of sessions outdoors seems to have speeded up that latter process. It can't ever be consistent but lacking a UV cupboard I'll try it again when I get the chance. English weather, sigh!

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"There is hope in honest error .... ". Charles Rennie Mackintosh.
http://www.ianchisholm.co.uk

I built my UV cabinet for under £50. I bought a cheap used single wardrobe, a couple of 2 ft UV strip lights and matching ballast.
There's not much else to it. Foil lined and a Baby bottle warmer to help maintain humidity, a few quid off the auction site. Doubles as a boiler for HHG.

All my acoustics have changed colour with aging, it's inevitable, only the rate changes.

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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 have to remember not to be sipping coffee when I open what looks to be a serious thread LOL

I'm sufficiently impressed with the results of exposure to sunlight that I may give that a go. And yes, I've already got the baby bottle warmer. Works a treat as a glue kettle!

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"There is hope in honest error .... ". Charles Rennie Mackintosh.
http://www.ianchisholm.co.uk

Get the relatively safe BL 350 UV lights. 350 refers to the light wavelength. BL is short for Blacklight. These are the type of tubes that printers use to dry their inks and are also used to zap insects. I have no trouble tanning soundboards or drying Oil varnishes with them. I'm pretty sure that the Ballast has to closely match the power of the tubes because they act as a current limiter. The wiring is simple, it's just the same as a fluorescent light assembly with the starter caps. In fact you may be able to use old strip tube assemblies if the wattage matches the UV tube - check on that.
You will need a few air vents as things can get hot inside a small cupboard. They should be baffled. I still wouldn't want to look at the lights directly.
I don't have mine sited in an outbuilding but it's probably a bit safer to do so, from a fire point of view. Not that it represents a great risk but the insurance company may not like the idea.

Has this set up been used with UV cure lacquer or UV cure polyester? Or is this just a heat booth?
Thanks

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Ken Cierp

http://www.kennethmichaelguitars.com/

Neither. It's set up for drying Oil varnishes and tanning wood. Heat is a by product of using two tubes that give off both UV and heat. The heat is largely unwanted, it's the UV that cures the varnish and tans the wood. I've yet to meet an Oil Varnish it does not dry (I've tried well over a dozen) , even when that Oil varnish has been applied directly onto Rosewood. Rosewood just takes longer.
BL 350 is classed as being UV -A and is relatively safe. My Violin making friend made a cabinet using UV -C and believe me, the lights came with some pretty stern and severe warnings. I decided to give that type a miss.
I've no idea what wavelength is suitable for lacquer, that may require a completely different UV wavelength. I suppose the manufacturer of the lacquer should be able to tell you which types of light cure the stuff.