Borax a as a wood stabilizer?


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Today the intern of my shop showed me the ribs of his newest viola. They had a nice yellowish brown color and he told me that he made it with soaking them in a Borax solution for 24 hours. He told me that he read somewhere that this treatment stabilizes the wood and makes it fire proof.

I had heard about this for making wood fire proof but can it stabilize the wood? Has anyone here experience with such a treatment and what were the results?

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Borax has been used many times by luthiers. It will keep the bugs or mold from the wood as well. But I would fear to soak thoroughly with any of these salts as they are hygroscopic and that may cause problems eventually. Salts usually have threshold RH above which they start sucking water from air (like 75% for table salt or 33% for magnesium chloride...) I don't know how much that may affect wod joints or dimensional stability but in this case I would go for as low concentration as possible.

I have no idea about stability... Perhaps they think it will work as a "buffer" at humidity changes?

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My understanding is that boric acid was used to treat wood even back in Stradivari's day, and so it is a plausible alternative to modern methods of preparing treated lumber. Like conventional wood treatments, it is aimed at preventing the wood from rotting and being attacked by insects.

As boric acid can be removed from wood by soaking it in water, however, if one is also going to get rid of hemicellulose by stewing, that should be done prior to boric acid treatment.

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5 hours ago, HoGo said:

 But I would fear to soak thoroughly with any of these salts as they are hygroscopic and that may cause problems eventually. Salts usually have threshold RH above which they start sucking water from air (like 75% for table salt or 33% for magnesium chloride...)

That would be a concern of mine as well. I haven't been able to find that relative humidity value for borax yet.

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In my early experimenting, I soaked wood in a borax solution, using vacuum and pressure to make sure the solution filled all of the cells of the wood.  After drying, the wood was slightly heavier, as you'd expect... but I have no way to tell how much was borax and how much was adsorbed water.

One thing I see is that borax usually comes as a decahydrate, with 10 water molecules attached... so I don't know how much more water it would be absorbing from the air.

Back to the treated wood... after drying, the wood was thermally processed, which shouldn't do anything to the borax itself.  I then had good data about the dead-dry weight, and therefore could calculate EMC accurately.  The borax treated wood had no significant difference from the borax-free wood. (however, a pin meter showed a high reading, which I attribute to some abnormal conductivity).

Bottom line conclusion (mine):  borax slightly darkens the wood due to slight alkalinity, adds a small percentage to the weight (depending on how much borax you try to get in the wood), but doesn't do a whole lot one way or the other.  I don't see how it would make the wood more stable.

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Borax is sodium tetraborate.  "20 Mule Team" is the natural decahydrate, and won't be hygroscopic.  Anhydrous (dehydrated) comes in two common formulations, the pentahydrate (which isn't really anhydrous), and the absolutely water free (expensive laboratory grade).   I've also seen a trihydrate mentioned in the literature.  Anhydrous borax is hygroscopic, and will suck water from the atmosphere until it reaches the decahydrate state.  Baking borax treated wood would reduce the hydration, and cause shrinkage as the crystals change shape, followed by rehydration from the atmosphere, which I would not expect to be a good thing.

Stradivari and his colleagues would most likely have had ready access to the decahydrate, which has been a common welding flux for blacksmithing since well before his day.

Boric acid is not borax, it's what you get by exposing borax to hydrochloric acid, and is not a salt at all, but a true acid.  :)

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1 hour ago, Don Noon said:

In my early experimenting, I soaked wood in a borax solution, using vacuum and pressure to make sure the solution filled all of the cells of the wood.  After drying, the wood was slightly heavier, as you'd expect... but I have no way to tell how much was borax and how much was adsorbed water.

One thing I see is that borax usually comes as a decahydrate, with 10 water molecules attached... so I don't know how much more water it would be absorbing from the air.

Back to the treated wood... after drying, the wood was thermally processed, which shouldn't do anything to the borax itself.  I then had good data about the dead-dry weight, and therefore could calculate EMC accurately.  The borax treated wood had no significant difference from the borax-free wood. (however, a pin meter showed a high reading, which I attribute to some abnormal conductivity).

Bottom line conclusion (mine):  borax slightly darkens the wood due to slight alkalinity, adds a small percentage to the weight (depending on how much borax you try to get in the wood), but doesn't do a whole lot one way or the other.  I don't see how it would make the wood more stable.

Thanks, Don. 

Saves me the time to do the experiments. 

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3 hours ago, Violadamore said:

Stradivari and his colleagues would most likely have had ready access to the decahydrate, which has been a common welding flux for blacksmithing since well before his day.

Boric acid is not borax, it's what you get by exposing borax to hydrochloric acid, and is not a salt at all, but a true acid

Well done 

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Borax has a Very long history as a woodworm treatment.

I would be very surprised if the Cremonese makers didn’t use it as a surface treatment. Equally their wood will have been cut from old growth in winter, then floated and ponded to prevent bluestain. This much is beyond dispute, since these practices died out within living memory.

So Andreas I’m sorry but the relevant experiment would be to follow these procedures and then see how things are holding up after 300 years ...

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5 hours ago, Violadamore said:

Boric acid is not borax, it's what you get by exposing borax to hydrochloric acid, and is not a salt at all, but a true acid.

And when I was looking up information about substances used as wood preservatives, it was boric acid, and not borax, that came up as one of the options, the others being long-named chemicals unlikely to have been available in Stradivari's day.

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7 hours ago, martin swan said:

Borax has a Very long history as a woodworm treatment.

I would be very surprised if the Cremonese makers didn’t use it as a surface treatment. Equally their wood will have been cut from old growth in winter, then floated and ponded to prevent bluestain. This much is beyond dispute, since these practices died out within living memory.

So Andreas I’m sorry but the relevant experiment would be to follow these procedures and then see how things are holding up after 300 years ...

That's a long wait, Martin. To join me for some beers in the meantime?

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12 hours ago, Quadibloc said:

And when I was looking up information about substances used as wood preservatives, it was boric acid, and not borax, that came up as one of the options, the others being long-named chemicals unlikely to have been available in Stradivari's day.

I believe some borax which has a pH of about 11 from memory is converted to boric acid inside wood (pH about 6.5)

Companies like this give a lot of information on borates .http://www.americanborate.com/all-about-borates/borate-applications/borate-wood-preservation/

Whether there is any crosslinking happening between borax and  extractives/wood cells  in the wood i dont know .If there is then there may be a stabilising effect.Im sure more google searching would give someone the answer.

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19 hours ago, Violadamore said:

Borax is sodium tetraborate.  "20 Mule Team" is the natural decahydrate, and won't be hygroscopic.

But is it deliquescent? (I think that might be the proper term for what HoGo and I were concerned about). Will a saturated solution absorb moisture from the air, if the relative humidity is above a certain level, like sodium chloride will?

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1 hour ago, David Burgess said:

But is it deliquescent? (I think that might be the proper term for what HoGo and I were concerned about). Will a saturated solution absorb moisture from the air, if the relative humidity is above a certain level, like sodium chloride will?

Borax comes in different forms some more hygroscopic than others .If it does turn into boric acid in wood ,then a simple wiki search gives this:

Preservation

Boric acid is hygroscopic, meaning it takes moisture from the air. This property allows it to prevent and destroy fungal growth in citrus fruits and rot in wood. In combination with an ethylene glycol carrier, boric acid can protect the wood against fungal and insect attack.[24]

 

But what if the boric acid reacts with the wood in someway would it still attract moisture???? (not sure) ,a borate specialist company like i mentioned above would proably know as no doubt they have researched it in detail.

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My grandmother used to hand wash her clothes and added borax to the mix and i still add a few ounces of borax in my laundry and often think how fortunate I am to be able push a button and a machine washes the clothes  clean instead of bending over on a scrubboard then rinsing and wringing dry and ironing with an iron heated on the stove.

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3 hours ago, David Burgess said:

But is it deliquescent? (I think that might be the proper term for what HoGo and I were concerned about). Will a saturated solution absorb moisture from the air, if the relative humidity is above a certain level, like sodium chloride will?

You mean doing the salt-in-a-puddle thing?  Nope.  Borax locks its water of hydration into the crystal pretty tightly.  It's less than a tenth as soluble in water as common salt, BTW.  To get it to dissolve well, it takes boiling water, and as soon as it starts to cool, the stuff will begin to crystallize out of solution, which makes it one of the substances used in children's "grow your own crystals" kits, as well as in demonstrating hydrothermal deposition to geology students.  Bear this in mind when trying to treat wood with it.  :)

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Did a crude experiment: Took 8 grams of 20 Mule Team borax from and opened box which had been stored at about 60% relative humidity. Exposed it to 100% humidity for 24 hours. Weight gain was .2 grams (unless it was the ziplok containment bag which absorbed the moisture and increased in weight).

Next, I might try to see if a saturated solution will maintain a certain humidity level in the bag. I'm doubting that it will though, since the borax showed no signs of clumping at 100% humidity. The salts I use for hygrometer calibration will "fuse together", or even collect some puddled moisture, if I expose them to humidity over their rated value.

Note: The borax might contain some sort of anti-caking agent like table salts do, but there is no mention of other ingredients on the box.

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29 minutes ago, David Burgess said:

Did a crude experiment: Took 8 grams of 20 Mule Team borax from and opened box which had been stored at about 60% relative humidity. Exposed it to 100% humidity for 24 hours. Weight gain was .2 grams (unless it was the ziplok containment bag which absorbed the moisture and increased in weight).

Next, I might try to see if a saturated solution will maintain a certain humidity level in the bag. I'm doubting that it will though, since the borax showed no signs of clumping at 100% humidity. The salts I use for hygrometer calibration will "fuse together", or even collect some puddled moisture, if I expose them to humidity over their rated value.

Note: The borax might contain some sort of anti-caking agent like table salts do, but there is no mention of other ingredients on the box.

The weight gain's probably from remaining impurities (such as salt), and any borax present that wasn't decahydrate to start with.  To my best knowledge, the decahydrate doesn't clump, but the anhydrous forms do (while converting to the decahydrate). :)

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On 5/29/2018 at 10:13 AM, David Burgess said:

But is it deliquescent? (I think that might be the proper term for what HoGo and I were concerned about). Will a saturated solution absorb moisture from the air, if the relative humidity is above a certain level, like sodium chloride will?

Borax is like ground sand or silica (the silicium equivalent), it is not hygroscopic. Boric acid however is massively hygroscopic, and hence an irritant to skin and eyes. And is is probably the altter that is used to treat wood.

My other concern would be that wetting the wood after all the effort to reduce its humidity, and then covering the wet wood with varnish, cannot be a smart idea. The Borax would either have to be applied before drying the wood, or in an oil matrix (like pummice in a ground).

I personally believe that boronic acid residues found on old violins come from floating the wood down rivers into Venice, where wood would have been traded in Stradivari's time.

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Borax occurs as a mineral that does not dissolve in water. Chemically it is similar to silicate, as B and Si are neighbours in the periodic system. Silica gel is a porous form of silicates. Boron does however have its very own chemistry due its 3-bonded nature.

The Borax that is sold as a liquid which I assume is a boric acid solution.

Sand consists of borosilicates, and glass consists of borosilicates.

Do you agree?

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