Borax/Boric Acid treatment fire retardant?

[DMcCoy]

This has been discussed here and else where as a preservative. 
My question does anyone know of research done where they test Borax/boric acid/antifreze solution that has been sprayed on(DIY) for fire supression?
I can find pressure treated studies and studies that correlate higher concentrations with higher suppression effect.

On getting best penetration one paper says spray it on green lumber only another says green or dry.
Help appreciated.
Thanks in advance

[Brad_bb]

I've never heard of it being fire retardant and I don't think it would be.  It's thin with no film thickness.  It dries.  It just keeps the bugs at bay as long at it doesn't get wet.

[Don P]

Actually it is also a fire retardant but I believe the loading has to be upwards of 4% of the wood weight. I don't think you can get anywhere near that with a non pressure treatment but am by no means certain of that, as in, I've never tried. I have left wood in the dip tray for weeks before but then never tried to burn it.

For the typical diffusion, DIY method of applying DOT, it penetrates much better green from the saw as opposed to applying it to dry wood. Rather than borax or boric acid, DOT is both, combined with water and heat, or you can buy it as straight DOT as Timbor (labeled for wood) or Solubor (labeled for ag fertilization), both of those are chemically identical.

As to the comments I see often repeated about borates simply rinsing off in the rain.  Do bear in mind railroad ties and utility poles can and have been borate treated. They are not keen on wasting their money.
http://www.aprailsupply.com/en/media/pdf/NSRTA.pdf

[DMcCoy]

That is a really good article!!!

They mention borate movement as being a positive.  My take away is that it moves deeper into the wood over time.

Borate treated wood is fire retardant, but all studies and youtubes appear to be PT.  If it moves over time as much as the RxR article implies and I apply it at high concentration I think it might work well for siding under an eve.

[GeneWengert-WoodDoc]

The borate for ties is applied first and diffuses into the interior of the tie where it would not be subject to washing away because they used creosote on the outside to act as a preservative and as a water repellent. So, the use of DOT for ties is entirely different than using it on lumber.  The tie treatment involved two preservatives.  The article cited is a research study. 

I have not seen commercial treatments of this sort, although I have not visited every tie treating plant.  The cost of a dual treatment would be higher (borate cost and increased time) compared to standard creosote-alone treatments.  Of course, predicted increase in tie life in zone 5, where decay shortens life to less that roughly five years, would indeed benefit.

If you use borates on the lumber and then sell the lumber, you are required to indicate that to the customer and must supply a CIS as well.

Note that green wood has little room for additional water.  Plus some species, like white oak and western hemlock, are so impermeable that the wood is incised to get channels into the interior.  Without incising or drying, any creosote preservative treatment will initially be on the surface only.  Such a surface treatment of borate or creosote, if covering 100% of the surfac and it does not get washed off, provides a barrier that will prevent insects and fungi from getting inside the wood.  The problem is that any end checks or surface checks or splits will expose untreated wood.  Borates, unlike other preservatives, actually diffuse into the wood through the cell walls, so, if the borate is applied to the surface and then the wood is covered with plastic to prevent leaching out while the borates diffuse, the borates will move or diffuse into the wood.

So, a deeper treatment with basically all preservatives except borates is obtained using drier wood.  Of course, this treatment on drier wood, if water-based, raises the moisture content, and often that means, because of the added water, additional drying and shrinkage after treatment.  Sometimes we see KDAT wood, kiln dried after treatment.

[Don P]

That is inaccurate. Notice the borate penetrated to the core of white oak heartwood without incising and there was "room". We aren't trying to raise the moisture content of green wood. Recall back to freshman chemistry, diffusion. The borate moves on the water from an area of higher concentration to an area of lower concentration seeking an equilibrium. The wood needs to be "wet" for this diffusion to occur, this is most easily done with green wood. As the paper noted when the wood was wetted the borate moved to the area in need, again diffusion.

Notice from the pictures with the curcumin indicator that borate has penetrated to the heartwood core of those very difficult to treat species. That is good news. Also notice it protected the steel spikes where with our modern ACQ treated lumber we worry about its corrosive effects on steel.

There are a number of similar articles to the one I posted above, all based on real world testing and actual use. Notice in the article above that they can lower the creosote loadings and still have superior results to a heavy load of creosote alone. Better for the environment and saving billions of dollars per year in tie costs. Again, they aren't keen on wasting money. This is Nisus' borate blend for RR ties;
http://nisuscorp.com/wood-preservation/railroad-ties-cellutreat

Borate only moves when the wood is above fiber saturation point, it moves on the free water that is within the cell lumen and not through bound water contained in the cell walls. Decay fungi are active where that free moisture is available to them for their life processes. Wood destroying insects can be active below that moisture level. Siding is protected by the eaves and the water repellant coatings applied after the borate. Actually not dissimilar to what the tie manufacturers are doing, get the borate in deep and then protect it behind a water repellant preservative. Siding and any above ground use within that envelope should not ever be above fiber saturation point if the building is properly detailed. That is why it is used in areas with high insect pressure. I have used the dissolvable borate rods in places that are not particularly well detailed and where there is a possibility of the wood wicking up rainwater and rising to high moisture levels, exposed log ends and post bottoms. Those rods are intended to dissolve and disperse through the wood if it becomes saturated. There are articles by the RTA on the efficacy of those as well.

I spent a month spraying a borate/glycol mixture on an 1840's log home during restoration after removing and replacing a number of rotted and insect infested logs. I was spraying as much as it would absorb twice a day before I let it dry and it would accept no more through that crystallized layer. I had gotten 75 lbs, or 750 gallons to soak in. If you think about the weight of the logs vs what I got in you'll understand that it was nowhere near fire retardant quantity. I do believe I get more in and deeper with a dip tray right off the saw as opposed to trying to rewet dry wood using a water/glycol mix, research also supports this.

[DMcCoy]

So here is what I'm finding for fire retardant.  Minimum of 7.5% add on.
https://www.fpl.fs.fed.us/documnts/pdf1990/levan90a.pdf

Western red cedar has a weight of 27lbs per cu ft wet and 23 lbs dry. 
I need to add 1.75 lbs per cu ft.
If my siding boards stacked are 8" x 12" x 8' gives me 5 1/3 cu ft needing about 9 1/2 lbs of boron in the boards. 

If I were to dip these when green how would I go about calculating the concentration to get 7.5%.
Weight of lumber plus weight of solution divided by total volume giving me weight 'x' per cu ft and go from there to get the lbs of borax/borate needed by total weight?

Thanks for all the links.

[DMcCoy]

I think I has settled on a course of action.  Strong solution of Borax/borate acid / antifreeze dip for 24hrs, followed by wrapping up wet in plastic for a week.  After drying surface charring with a propane burner to provide some waterproofing.
https://en.wikipedia.org/wiki/Yakisugi

Will see how this works. 

[Brad_bb]

So after all that, I take it the answer to the original question is "No".  DIY spraying of borate products will not make the wood fire retardant, correct?

[Don P]

By strong solution you need to be careful with concentration and temperature, you'll be venturing into uncharted territory for me. At 1 lb of DOT (Timbor or Boracare) per gallon of water you have ~10% solution which is stable down into the 40's F. For relatively short term the borate stays in solution. At 1.5 lbs/gal, ~ 15% solution, as soon as it cools (I prefer to mix with warm water if possible) it begins forming crystals and you end up basically making rock candy as it precipitates out of that saturated solution. To maintain the 17% solution they are calling for would require keeping the solution warm, how warm I don't know. I've seen mention of higher concentrations than that held at 140°F. Somebody you know got a sous vide kit for Christmas and is going to be done playing with it soon  :D

When you are done with the solution in the tank, cut it to stabilize, filter into a sprayer and hit your framing or other wood that will benefit from it. In other words don't store it for a rainy day, you'll have that chunk in the bottom. Which can be boiled back into solution but use it once you mix it is better.

The only way I can think of to know the approximate loading is to run some representative control samples and in the end at the same moisture content make identical sized samples, weigh and figure out the math. As a practical matter the loading isn't what you are interested in, I'd torch some samples, that is the real goal. You aren't marketing anything here. I do recall one of the treaters on the Nisus link did have a frt in their web address, fire retardant treatment, might be worth a visit to their site.

Don't forget ethylene glycol is a flammable alcohol. I cannot speak to the others but would assume so, edit MSDS' say yes. If you are working with green stock I'd skip it. I tend to go as light as possible with it, there is nothing magic going on there it is simply a very slow drying ... "water".  Any glycol will perform the wetting role. If you are playing with EG it is a good idea to stock a bottle of high proof vodka or similar as an antidote. I wonder if old time painters came by their reputation honestly.

A very small amount of dish soap, drops per 5 gal bucket not foam, will act as a surfactant helping to wet out the wood.

At that loading you'll definitely have crystals on the surface. I've wiped or sanded that off prior to finishing. I suspect there will be a learning curve with the sho sugi ban.

One more for the experimenters box, look into waterglass, sodium silicate solution.

Good luck, I'd like to hear how it goes

[DMcCoy]

Thanks for all your help.  I'm more than happy to skip the anti-freeze part, I don't enjoy handling the stuff.  The surfactant wasn't something I had thought of. I will do some trials before I get too far..

Brad - There are several you-tube's with spray on fire retardants that work to varying degrees.  Not all manufactures will link their MSDS or SDS on line so it is hard to tell if there might be borate's used. Borate spray treatment seems simple enough but open research is somewhat lacking perhaps due to its solubility,  ineffectiveness as a spray, or application issues for uniformity as a spray.  In the opening paragraphs of the link I posted there is a sentence that mentions borate treated wood exposed to fire forms a seal against allowing volatile gasses to escape.  I read this as a potential as a surface treatment but cannot find that specifically.