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Sun tanning your instrument

MJ Kwan

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Tanning with sun is something that can be dangerous to the health of the instrument if not done properly. First I would say that using uv lights is a safer way to get the tanning effect, that being sad, to tan outside it must not be too hot, the instrument should be hanging, hopefully with a slight breeze in order to self rotate. Cloudy days that are not damp are good days as the tanning will happen without direct sun.


Basically if you put it out on a hot day, in direct light, and then walk away, do not be surprised if a plate pops off the ribs and opens up a seem. The internal temp goes way up inside the box and can be hot enough to warp wood or pop seems, so caution is suggested

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Thanks yall.

And what about your lower limit of humidity and temp? (I'm in Chicago)

Can anyone give rough equivalents of time in lightbox vs time in the sun (or out on a cloudy day, etc)?

Better yet, anyone have comparison images?

Does the color result come out the same after lightbox and after sunning?

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Colour on maple from UVA tubes is more yellow than colour from sun. 
If you use hot water you can actually wash some of the colour off too...
as I found out when washing off some glue on a back that had been tanning. 
San tanning is better since it's cheaper and less toxic. 

Hard to make direct comparisons with sun and UVA tubes when 
working with time and colour, because it depends how many tubes
you use, how many watts they are, how much UVA is in your sun
(more if you live in the Himalayas) and how much colour you actually want. 

I have 20 tubes which put out lots of light, some instruments left in the room
for a month using 8 hours light per night come out golden coloured. 
Not good to put ribs in hot light rooms when they're off the forms, they 
will distort badly becoming skinny. Things generally shrink a bit too...
fingerboards and necks need to be re-finished etc. 

Generally, it's all a bit of a pain and if you can avoid it all then do. 


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I don't tan in the sun because I've been told that it reduces the luminosity of the wood. You'll get less of the holographic effect of the flames as we'll. The tanning will make it easier to control the color, though, so it spends on where your priorities are.

I do use sun for drying varnish, and I only leave it outside in 50-75 degree weather. Beyond that I leave it n a window indoors with a reflective surface behind the instrument. We don't get dry weather in the summer, but I wouldn't leave it out below 35%RH. This summer was extremely humid and I regret not dehumidifying the shop. I had some issues with the instrument I made during that period. Not sure the exact RH, but I think it hung out around 70%-80% for a few weeks.

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Here.  All the time.



I definitely do not recommend what I have done on occasion on the cooler days here to make varnish dry faster... adding solar reflectors.  It is probably my aerospace testing background, where you usually test things far, far beyond where they will ever be used.  I figure if it doesn't fail at 145 F (observed surface temperature), it will probably survive most things later.  And I'd rather have something go wrong here than there.

But, like I said, I'm not recommending this to anyone.  My processed wood is also far less sensitive to this type of abuse.

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I like to put my violin out in the sun to harden the oil varnish, seems to be much faster than my uv tanning booth.  However, weather changes fast here in NC mountains, so I never leave home with it outside, and never overnight (duh!!).  I think 50 - 80 degrees would be OK.


 I did once put a violin out in strong sun that I had just varnished with a SPIRIT varnish, and in moments it started to blister -- had to strip and start over.  

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Beautiful ground colour Huslar!


It's so lovely to varnish over a naturally rich ground. I was told that the Mittenwald students hung their violins in the sun until their final year, when they varnished them. I know one maker who I think has one of the best varnishes I've seen, who hangs his for several years.


I've never had time to do that, but I'm trying to work towards it. Really, if you decide that you're just doing the woodwork, and hanging the thing up, it doesn't seem like such a time commitment.

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I use to hung my white violin at the sun but I learned to be careful with the hard direct sun because a centre joint was opened one time ago. My latitude is 34,5° south.

Now I hang the instrument early in the morning and in the last hours, always checking the temp of the wood.

I saw that in the middle shadow at the open air also we achieve some colour.

When I varnish I consider the hour. Three hours of sun for drying quickly  speed up the process helping me a lot.



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