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Much has been said about the importance of keeping the relative humidity at a safe level. Some say it should be between 30% and 40%. Others say between 40 and 50. However, it strikes me that the optimum relative humidity should be that which existed at the time the instrument was assembled. If the wood came to equilibrium with the vapor pressure in the atmosphere before assembly, as long as the assembled instrument stayed in that room what difference would the exact value make? When the instrument leaves that room, everything varies. So in the absence of knowing what the original conditions were, why wouldn't it be just as dangerous to keep a humidifier in the case? 

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I believe that museums strive for between 40 and 60% RH. My house is really weird in that it stays at almost exactly 50% all the time according to multiple hygrometers. One problem is hygrometers are notorious for being inaccurate!.

DLB

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I believe that museums strive for between 40 and 60% RH. My house is really weird in that it stays at almost exactly 50% all the time according to multiple hygrometers. One problem is hygrometers are notorious for being inaccurate!.

DLB

i give you also the gospel of Saint Burgess 

 

http://www.burgessviolins.com/humidity.html

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Seeing that instruments are not assembled instantaneously, trying to pin down the RH that the instrument was assembled at is a fruitless exercise. I don’t know anyone that recommends a 30-40% range.40-60% RH would be more typical.

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That's exactly my point. It could be anything. The question is--why isn't that relevant? Assuming a  RH somewhere in the  30s when assembled, why wouldn't a RH of 50% be harmful later? As to 30-40%, I thought I saw it somewhere on  this forum--but even 40-60 as you suggest is huge. I once  had a table split after the RH went up to 60 and then back down to the low 40s-.

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13 hours ago, Sheldon Weiner said:

Much has been said about the importance of keeping the relative humidity at a safe level. Some say it should be between 30% and 40%. Others say between 40 and 50. However, it strikes me that the optimum relative humidity should be that which existed at the time the instrument was assembled. If the wood came to equilibrium with the vapor pressure in the atmosphere before assembly, as long as the assembled instrument stayed in that room what difference would the exact value make? When the instrument leaves that room, everything varies. So in the absence of knowing what the original conditions were, why wouldn't it be just as dangerous to keep a humidifier in the case? 

Sheldon, yes, it would probably be better to keep a violin in the same relative humidity as that in which it was assembled, assuming that the maker has kept the humidity constant during the various assembly steps, and has made sure that the wood has reached, maintained or reestablished equilibrium moisture content, after processes involving application of moisture are used.

However, maintaining a super-tight humidity range is almost impossible when a violin is actually used out in the real world. Even if the violin is kept in a room where the humidity does not vary, an instrument is in a much more moist microclimate when it is brought close to the human body for playing.

The main reasons I recommend a range of 40-60% are that it's reasonably doable; instruments are very unlikely to sustain damage if kept within a 20% range; the upper level (60%) is below the level at which instruments become much more "plastic", and susceptible to permanent deformation from string load.

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"I once  had a table split after the RH went up to 60 and then back down to the low 40s-. "

I think that your table must have had other problems, like poorly seasoned wood, or non-sliding cross braces. In one of my other lives, I build furniture, and have never had anything split. Many people's houses run (not recommended) from low teens %RH in the winter, to really high humidity in the summer, without having their furniture split apart. Unless you have some kind of super controlled house, your humidity range almost certainly exceeds a 30-60% range. Historically, temperature and humidity control is a pretty recent development. Strad was pretty much at the mercy of the environment. Expecting to tightly control the humidity of a working instrument is a fools errand. The 40-60% RH is a nice goal for storage, but when it's out being played, anything goes.

 

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3 hours ago, FiddleDoug said:

Strad was pretty much at the mercy of the environment. Expecting to tightly control the humidity of a working instrument is a fools errand.

In the aerospace biz, you always subject your stuff to a more extreme environment in testing than it is meant to see in actual operation, so you know it won't fail later.  Although high humidity is not great for glue, the main concern is cracks, which as far as I know only will happen when the humidity is low (or the instrument is very hot... which is the same thing).

So I'm not that careful about maintaining humidity in the lightbox, as I'd rather see a failure now, rather than having it happen after the client gets it.  And using water to raise the grain or a water-based coating or size like casein will sent EMC higher than you're ever likely to see, which is also a nice test.

To avoid cracks later, it would seem best to assemble the instrument (specifically, gluing on the plates) at low humidity, and live with the non-catastrophic distortion of higher humidity.  I'm not sure how well-controlled that can be, give that we're dealing with hot, water-based glue to attach the plates.

Of course, the best solution would be to use wood that doesn't expand or shrink with humidity changes, and torrefied wood gets 40% of the way there :).  We won't mention that it's more brittle, and might crack with less stress... but there have been no cracks as yet.

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I misread a Kreit quote once saying 27 F would bring wood down to 0% mc. 

For some reason I read it as 7 F so proceeded to put glued together boxes outside for a few days when temps were 5 F.  No damage that I could see.

Where I live I like gluing wood from 27 to 35% humidity.  I like working wood with tools the best at real high humidi  I just has a wild feral kitten run across the keyboard - forgive any goof ups typing wise.

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20 hours ago, Sheldon Weiner said:

When the instrument leaves that room, everything varies. So in the absence of knowing what the original conditions were, why wouldn't it be just as dangerous to keep a humidifier in the case? 

Even if I knew the original conditions I would do the thinking of how much moisture does an instrument need.  An example can be like today where I'm at, let's say a cross town trip is in order to a violin shop.  The readings for humidity on an hourly basis is from 50% to under 70 % for the rest of the day - long story short, I would still have a humidifier along because of the old saying "it's better to have it and not need it than to need it and not have it"   Surely the last week of October here {rain mostly} would be a totally different story. 

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1 hour ago, uncle duke said:

Even if I knew the original conditions I would do the thinking of how much moisture does an instrument need.  An example can be like today where I'm at, let's say a cross town trip is in order to a violin shop.  The readings for humidity on an hourly basis is from 50% to under 70 % for the rest of the day - long story short, I would still have a humidifier along because of the old saying "it's better to have it and not need it than to need it and not have it"   Surely the last week of October here {rain mostly} would be a totally different story. 

I wouldn't consider a humidifier to be beneficial in any way, at a relative humidity level of 50 to 70%. At that level, adding moisture is more likely to harm the instrument, though not as obviously and dramatically as too low a moisture level.

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David, I think that you answered my question. The ideal situation would be to have the instrument stay in an environment in which it was made. That being impossible, the 40-60 range is recommended because most instruments can take it and it is doable. 

Don Noon Your practice of gluing on the plates at low humidity makes perfect sense to me since most problems seem to arise at lower humidity than when the plates were glued.

Uncle Duke: I'm happy with your gluing at between 27 & 35, which is consistent with  the two above.

 

My question had to do with how the original conditions would relate to the instrument's behavior under conditions of actual use. You all answered to the point Thank you.

 

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35 minutes ago, David Burgess said:

I wouldn't consider a humidifier to be beneficial in any way, at a relative humidity level of 50 to 70%. At that level, adding moisture is more likely to harm the instrument, though not as obviously and dramatically as too low a moisture level.

What would be best with 99 f. in the shade, 130 heat index and 50 % humidity, which is what is here now as I'm typing?  And the appointment needs to be kept, for example.

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26 minutes ago, Sheldon Weiner said:

Uncle Duke: I'm happy with your gluing at between 27 & 35, which is consistent with  the two above.

Those two guys have told me at one time or another to don't glue at those lower readings.  There have been others that mentioned that too.  Just wait for the 40's minimum.

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As a former environmental controls engineer for a museum, you aim for two things:

A reasonable level around whatever has been "normal" over the life of the artifact.

Tight control over the range of fluctuation and rate of fluctuation around "normal".  Rate of fluctuation is extremely important.  

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14 hours ago, Peter K-G said:

The wood will be like a sponge, sucking up the water and gel the glue and starve it. Tried many times it always fail

Can add a round of hot water to the glueing surfaces before adding the hot water glue mix itself. 

Edited by Anders Buen
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3 hours ago, Peter K-G said:

The wood will be like a sponge, sucking up the water and gel the glue and starve it. Tried many times it always fail

With a hot hide glue and water mixture, I have never noticed any indications of the water going into the wood any more or less than the mixture. If you have, please describe how you came to that conclusion.

 

In my experiments, a good quality hot hide glue does not release or soften at 100% humidity. It requires the application of liquid water to do so.

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Well, if you need to be picky

"sucking up the water" => sucking up the glue mix

"The rest of my post" =>

Rephrased:

I find it difficult to glue in low humidity conditions, especially when the wood is close to 0% MC. I haven't been able to glue a strong joint yet in such environment.

A strong joint on the other hand doesn't come un glued even after steaming a plate or pouring hot water on it, it also seems to tighten it.


 

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43 minutes ago, Peter K-G said:

Rephrased:

I find it difficult to glue in low humidity conditions, especially when the wood is close to 0% MC. I haven't been able to glue a strong joint yet in such environment.

A strong joint on the other hand doesn't come un glued even after steaming a plate or pouring hot water on it, it also seems to tighten it.

I have never tried to glue at 0% MC, oven dry. But I am pretty sure I´ve glued parts at around 6% MC, which is not unusual through the late wither here in Norway. However, if the fiddle should go to a more humid region of, say, USA, it should be assembled at a higher MC. I think David B advice is good to follow then. Maybe around 40% RH is good.

I think the wood very soon reach 100% MC close to applied glue. If a little hot water is applied before, the wood becomes hotter, can hold the glue liquid a bit longer, and the hot hide glue does not dry as fast. Some applies hide glue to the blocks and let it dry before doing the full glue job.

Glueing at 0% must be something experimental. I cant see any good reasons to do so. 

I think Don Noon with his low MC torrified wood is more used to very low MC wood glueing. I think it is about half what is normal, but it does creep upwards over time. Maybe it reaches normal level again at some time.

The MC up to about 30 % is «dry» bound in the cell walls. Free water in the cells happens above that. Glueing adds some free water in the glue gel. A bit of both may happen, some picked up as dry some stays in the near glue joint cells for a while. 

Edited by Anders Buen
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It's between 40% and 60%. I always try to keep my room under 60%, I use a dehumidifier all day when I'm not in the room. Outside it's always 70%-100% all year.

I have a good case with great isolation, if I close the case at let's say 57% humidity, it will keep that level of humidity inside for many days or weeks, even if the case goes to more humid environments. Obviously for this you can't use wooden cases.

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18 hours ago, Peter K-G said:

The wood will be like a sponge, sucking up the water and gel the glue and starve it. Tried many times it always fail

Handy tip:  glue size first.  I always do.

The endgrain of the blocks will suck up glue and give a poor joint if you don't glue size first, no matter what the humidity is.  For the plate itself, well-cut spruce won't suck up glue or water, other than the first cell or two of thickness.  I size it anyway.

The danger then of gluing in low RH is that the water evaporates rapidly from the glue surface, drying and cooling the glue before you can get the joint together.  I think this too can be worked around, by adding hot water with a thin blade before tightening the clamps.  This is a bit difficult to do at the neck block, so I make sure to apply the glue last and clamp first there.

 

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