Hi Folks...
This topic has been all over the place, and I even get lost myself sometimes...so...I thought I would start this
thread so folks can come here and get some of the "knows" of this vast and varied subject. Folks coming here can ask specifics and share new information if they find any so we can all learn....
I will start with a little validation...I have not seen anything "new" in 40 years of doing woodworking, and related fields of different professions I have worked in, that isn't just a "remake" of something older...Wood rots under certain conditions, and won't under others. Put
wood underwater it will last 10,000 years or more if kept from perhaps any "sea going" and other pelagic 'critters' that like to borrow in it. The best wood working wood is "water logged" logs that get milled and air dried. These are much more stable, last longer when exposed and just seem to be better all the way around...If wood gets wet...it just needs to dry thoroughly and quickly or it will begin to decay. Some species much less than other...but all will rot eventually under a 'wet-dry cycle' when exposed to fungi or other wood loving organisms. I have even been lucky
enough to have some deep conversations with Dendrologist that actually do nothing in there life but teach and study how long it take for wood to rot...I even follow one of the fine folks to look at a 'stump' that had been rotting for over 700 years...Like I said...some species take a long time...
So we have a choice...Design mechanical systems of joinery that allow wood to stay dry or get wet and then rapidly dry out or we can 'poison' the wood...Combined the two (chemical - mechanical) and we have an even better system (if it is needed.)
Now for the 'poison'...we can go with the "real poisonous" stuff that kills everything (including us and the environment around it) or we can chose other systems that are much less toxic. Being a traditional-natural builder, and ecologist...I chose the later...and of these we have topical and internal methods with the second being virtually impossible to achieve effectively so we will focus primarily on the first.
External Surface Treatments are broken down into topical liquid applications of minerals, oils, and botanicals, and mechanical structure change...These liquid forms are acidic, base, and polymer barriers for the most part some actually molecularly bonding and/or changing the structure of the wood so as to render it less prone to attack by decaying organisms. The mechanical is a carbonizing which I covered in the post thread titled
Yakisugi (grilled cedar) 焼き杉 - Charring Wood as a Finishing Modality.
So lets move into these treatments as they are available to use today.
Oils come in many forms. Of the types used in 'preserving wood' Cedar Oil and Pine Tar Oils are the most common and effective though there would seem to be other proprietary varieties that are employable but much less common or easy to obtain and work with. Some products are heavily industrialized with additives and are very toxic! All natural "drying oils" (i.e.
flax, tung, walnut, etc) have some positive effects all by themselves. Pine Tar Oil is probably one of the best and oldest yet does drastically changed the color of wood.
Next we move into Botanical formulas and their proprietary manufacture. These blends, by themselves are not that good, all have "repelling" or inhibiting elements. Yet by themselves are not worth going into nor are any of the formulas available for public knowledge anyway as most are family or copyright protected. I know many of these as a singularity they do not work for long as they do not have the durability or effects that just oils alone would.
Next, and the largest most effective group of natural treatments...minerals. These are predominantly different varieties of mineral salts...some can be very toxic in various concentrations, and here I will try to not recommend but suggest and offer for consideration different brands one may chose to try.
Please note these are not recommendation or suggestions just information...
Two of the most common that have been around my entire life are
ECO Wood Treatment and
Life Time Wood Treatment. Both...can be...effective or partially so...both are more hyped than well described...They are both "proprietary" formulas that have both minerals and other botanical elements in the formulation matrix. The MSDS for both (
EWT MSDS and
LTWT MSDS) do not give specifics and there is both lawsuits and other legal regulations about this. They keep it all at bay because those of us that learn more about them are simply not that impressed.
Do they work...well I would have to say yes they do...on some woods better than others and some very well. However they drastically age the wood and change its appearance drastically to an off gray to green to even black patina, and this was the first clue to what is the primary "chemistry" that is going on with these to products.
I am certain (now basically know) that these products contain some form of iron salt (
iron sulfate) and is the same or chemically similar to each other. The MSDS for both do not give the exact ingredients, nevertheless the decomposition byproduct is listed is
Sulfur Dioxide (SO2). SO2 is a decomposition byproduct of Iron Sulfate. Iron Sulfate is used as a chemical dye, reacting with mordants such as tannic acid found in tannin rich wood species thus forming a compound called iron tannate yielding a silvery gray to brown to almost charcoal appearance based on solution strength and tannic acid levels in the wood being treated. Iron Sulfate is also used as a
lawn application to control moss, so I would suggest that it's preserving properties would relate to Iron Sulfate possibly inhibiting the growth of wood decaying organisms such as moss, algae, and fungi on or within the wood. I could go on...but the primary information is covered and the bottom line is this is a preservative just like many others, it does work, but is not the "holy grail" that advertising makes it out to be. Again...good design and traditional modalities are of equal or better value and these are only a simple augmentation to traditional methods.
Here is a good place to share an old text that
should be in any traditional builders library:
The French Polishers Hand Book copyright 1910 It also mentions sulphates of iron or 'green copperas' which is also (or a family of salts there of) in the two products referenced above.
The next big group is the
borates.
Armor-Guard Borate Wood Preservative is one of the most common of these products with its MSDS found
here. Its active ingredients are
disodium octaborate tetrahydrate (also know as
boron sodium oxide) is an
alkaline salt also and is not to be confused singularly with '
boric acid.' The advantages of this algaecide, fungicide and insecticide is these salts are much safer over conventional pest control and fungal treatments They are well studied and are non-carcinogenic and has a low toxicity to humans and pets. It is also odorless and proper application lasts for the lifetime of the wood. Repeat treatment is not usually necessary. It is best used during new construction as this is the opportune time to reach all areas effectively.
Boric acid and
borates in general, unlike most industrialized pesticides and fungicides are common naturally occurring compounds. Like most pesticides however, they can cause health problems if an individual is overly exposed. Laboratory studies have identified a variety of health effects caused by exposure to these compounds, particularly at high doses rates. Yet this can be said of over exposure to Cedar oil which is highly toxic as many botanical compounds are. At the same time, boron is an essential nutrient for many plants and other living things. Bottom line...too much of anything is bad!
With any of the above materials common sense, following directions and/or professional assistance is strongly advised!
That should be good for now. I will add more as I filter through my files and
books and folks 'jog' my memory with questions....
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