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Flame Stopping Stain Additives

We're looking for a flame-stopping additive to mix in with oil-based stain so we can stain our church building, which has cedar clapboard siding. We have the stain, but can't find the additive. Suggestions?? Pilamiyaye! / thanks!

Re: Flame Stopping Stain Additives

Are you SERIOUS?!?

...it's called a sprinkler system!


Re: Flame Stopping Stain Additives

There are flame retardant paints, but I have never heard of an additive which retards flame in stains, especially oil stains.

Re: Flame Stopping Stain Additives

check with a paint supplier that deals specifically to contractors

Re: Flame Stopping Stain Additives


My understanding suggests to me that the additive you're looking for is called alumina trihydrate, and it's available from Huber Engineered Materials:


That same chemical goes by many names, including: Aluminum hydrate; Aluminum trihydrate; Aluminum (III) hydroxide; Amorphous alumina and Trihydroxyaluminum. It is a highly transparent white powder:

By "highly transparent white powder", I mean that alumina trihydrate is a highly transparent material (like ice or salt), but becomes opaque as a powder only because of the scattering of light by reflection and refraction at each solid/air interface when it's in the form of a powder. So, just in the same way that water is transparent, but clowds are opaque, alumina trihydrate is transparent, but when ground into a powder, it becomes opaque only because of the scattering of light. Just like salt.

It has a chemical structure like this:

Essentially, it's three water molecules loosely bonded to a central aluminum atom. And, because of that chemical make up, it works exactly the same way as gypsum (CaSO4-2H2O) in drywall. That is, in the event of a fire, the bound up water (H2O) molecules in the gypsum are driven out of the drywall in the form of steam, thereby keeping the temperature of the drywall core (and everything behind it) at 100 degrees Celsius until the entire gypsum core of the drywall is reduced to calcium sulfate, which is a white powder. It's only when there's no more bound up H2O in the gypsum that the wooden wall studs are exposed to the full temperature of the fire and begin to burn. In this way, drywall is effective in preventing the rapid spread of fire inside a house, giving the occupants more time to escape.

A good analogy is that of a boiling pot of water. No matter how hot the heating element under the pot gets, the water will never get hotter than 100 deg. Celsius. The hotter the heating element, the faster the water will boil, but it'll never boil hotter than 100 deg. C. Since wood has a kindling temperature of 300 deg. C., the wood studs in the walls won't start to burn until all the water in the gypsum drywall has been converted into steam. So, the additional time it takes for the water in gypsum to boil off translates directly into addition time that the occupants of the house have to escape.

Alumina trihydrate works exactly the same way. In the event of a fire, the wood under the paint containing alumina trihydrate won't get any hotter than 100 deg. C until all of the bound up water in the alumina trihydrate is driven off. However, keep in mind that gypsum drywall is 1/2 inch thick, whereas the film thickness of your stain is gonna be a few hundredths of an inch. In that case, the effect of the alumina trihydrate on the rate of fire spread is likely to be minimal because of the very thin film of protection covering the wood. In order to make a significant difference in the rate of fire spread, you'd need to mix alumina trihydrate into your oil based stain until it was thick as porridge, and then spread it onto your cedar siding with a trowel instead of a paint brush.

Hope this helps.

PS: You don't need to know the rest...

Alumina trihydrate is the difference between Plexiglas and Corian (fake marble). Corian is made by mixing alumina trihydrate into acrylic resin and casting that slurry into slabs (with built in bathroom sinks). The result is a white-ish coloured slab that looks very similar to white marble.

From Huber's web site:

Re: Flame Stopping Stain Additives

You should consider treating the siding with a sodium borate solution. Sodium borates are used as a fire retardant in cellulose. Cellulose is shredded newspaper. In addition to acting as a fire retardant, it also repels or kills insects and borers, including Formosan Termites and Carpenter Ants. It also stops and prevents mold, mildew and rot.

One solution you might use is called Timbor. You can mix it with water or an antifreeze/water solution and apply with a garden sprayer. You can also mix your own by mixing 2 parts boric acid with 3 parts 20 mule team borax. Boric acid is sold as a roach killer.

You mix about 2.5 to 3 lbs. of powder to a gallon of water. The hotter the water, the easier it mixes. The downside to this stuff is that it is water soluble, but you are staining the wood after with an oil based stain.

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