1. What is Chemonite®?
Chemonite is the registered trade name for wood treated with ACZA (ammoniacal copper zinc arsenate), a waterborne wood preservative. Pressure treating wood with ACZA protects it against marine borers, insect attack and decay. First developed at the University of California in the 1920's, ACZA was commercially developed for the treatment of coastal Douglas fir and other hard-to-treat species in the 1940's by J.H. Baxter, a California wood preserving company.
2. How is the wood treated?
First, tiny cuts called incisions are made in the wood. The wood is loaded on carts and pushed into a large steel cylinder. The cylinder is closed, vacuum is applied to remove excess air and moisture from the wood cells, and the preservative solution is pumped in. Pressure and heat are applied to force the solution deep into the wood cells. The required penetration depth ranges from a minimum of 3/8 inch on 1" x 4" lumber up to 3/4 inch for a 12" x 12".
3. Will the chemicals wash out in water or in the ground?
Chemonite wood is very leach resistant. The U.S. Environmental Protection Agency (EPA) has stated that "Arsenicals in treated wood have a very low tendency to leach into the soil..."
4. If it doesn't leach, how can it be dissolved to get into the wood?
The preservative is dissolved in an ammonia solution for the impregnation process. After treatment, the ammonia evaporates causing the preservative to precipitate in solid form within the wood cell structure.
5. Does treatment change the color of the wood?
Yes, most preservatives do. Chemonite wood takes on an attractive, greenish dark brown color because of the copper compounds in the preservative. The color is difficult to control. Sapwood will tend to be greenish brown with heartwood tending toward more brownish black. Over time, the color becomes more uniform.
6. Does Chemonite wood have an odor?
Only when freshly treated. Once the ammonia evaporates in a week or two, the treated wood is virtually odorless. (Avoid storing any freshly treated wood in damp, unventilated facilities.)
7. How do I treat "end-cuts"?
Minimize any cutting to obtain the maximum benefit of the treatment by not exposing untreated wood to decay hazards. If you do cut Chemonite treated wood, however, the exposed areas can be protected by applying copper naphthenate solution or other solution containing at least 1% copper—available over-the-counter at most home centers. Use a generous amount to completely cover any untreated areas of your project exposed by cutting or drilling.
8. Does Chemonite wood present a safety hazard?
Wood treated with Chemonite falls under the U.S. Environmental Protection Agency's (EPA) minimum protective precautions. Other than the normal safety measures suggested for handling any wood (wear gloves when handling, goggles and a dust mask when drilling or sawing), no special handling or clothing is required. See the Consumer Safety Information Sheet.
9. Does the treatment affect the strength of the wood?
No. The National Design Specification allows the same strength values for treated as for untreated lumber of the same species, grade and moisture content. However, when incised, the incising factor should be applied.
10. Do nails hold well in Chemonite lumber?
Laboratory tests and field experience indicate that nails hold just as well in Chemonite lumber as they do in untreated lumber. For fasteners and connectors, always use hot-dipped galvanized, stainless steel or an approved equal.
11. Can Chemonite wood be painted? If so, how soon after treatment?
Yes. Simply follow the manufacturer's instructions. The wood should be clean and dry before painting. As with any wood, Chemonite wood should be dried to 20% moisture or less before paint is applied.
12. Does treatment affect the flamespread rating of wood?
Actually, Chemonite wood is slightly more difficult to ignite than untreated lumber. Tests conducted at Underwriters Laboratories Inc. confirm the fire resistant qualities of Chemonite wood:
| • Douglas fir lumber treated retaining 0.35 pcf of ACZA showed a 41.7 flame spread rating, which indicates a Class B/Class II fire retardant rating. |
| • Douglas fir lumber retaining 1.86 pcf of ACZA showed a 24.8 flame spread rating, which indicates a Class A/Class I fire retardant rating. |
13. How long will this treated wood last?
Thirty to fifty years or longer, depending upon the end use and barring any incidental damage.
14. Will Chemonite wood last if it's buried in the ground?
Yes, wood treated to a minimum 0.40 pcf retention will withstand wood-destroying organisms in ground contact.
15. Is Chemonite wood suitable for aquatic applications?
Yes. Treatment in accordance with AWPA Standards provides long service life. Specifying that the wood conforms with the best management practices of the Western Wood Preservers Institute (WWPI) ensures that Chemonite Wood is suitable for use in aquatic environments.
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16. Does wood that is "Treated to Refusal" meet building codes?
This phrase--Treated to Refusal--indicates that the wood was treated under specified conditions until it refused additional preservative, a point usually below the requirements of industry standards. The result is wood that cannot be relied upon to last as long as wood that meets standards. Such wood does not comply with model building code requirements for treated wood. One reason for substandard material can be use of a preservative other than ACZA which is not suited for refractory (i.e., difficult-to-treat) species.
To assure yourself of properly treated wood, look for the logo of an ALSC-accredited inspection agency on lumber tags or ink stamps. The logo often appears beside a checkmark symbol.
17. What are incising and penetration improvement methods?
In many western species, penetration improvement methods are employed to improve the depth and uniformity of preservative penetration into wood. Most commonly this is seen as a pattern of slits ("incisions") on the surface of lumber. Full-length incising and deep-incising are other methods, as are radial-drilling and through-boring, used mostly for poles and piling.
Although these methods can improve preservation, they can result in a strength reduction for the wood, depending on the pattern, size, and number of incisions. When treated sawn wood products have been incised, the reference design values most be multiplied by the incising factor, in accordance with section 4.3.8 of the National Design Specification for Wood Construction. A review of penetration improvement methods is recommended for insertion into a specification.
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