Treatability of Underutilized 

Northeastern Species with 

CCA and Alternative Wood 

Preservatives

Stan T. Lebow

Steven A. Halverson

Cherilyn A. Hatfield

United States

Department of

Agriculture

Forest Service

Forest

Products

Laboratory

Research

Note

FPL–RN–0300
November 2005

Lebow, Stan T.; Halverson, Steven A.; Hatfield, Cherilyn A. 2005. Treatability of underutilized northeastern species with CCA and alternative 

wood preservatives. Research Note FPL-RN-0300. Madison, WI: U.S. 

Department of Agriculture, Forest Service, Forest Products Laboratory. 5 p.

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Abstract

Opportunities for use of northeastern species such as balsam 

fir, eastern spruce, eastern hemlock, and red maple could be 

improved if these species could be adequately penetrated 

with preservatives and subsequently shown to be durable in 

outdoor exposures. In this study, specimens cut from lumber 

of northeastern species were pressure-treated with either 

chromated copper arsenate type C (CCA-C), ammoniacal 

copper citrate (CC), alkaline copper quat type C (ACQ-C), 

or copper azole type A (CBA-A). Treatability was assessed 

by measuring retention and penetration of preservative. The 

results indicate that the arsenic- and chromium-free alternatives to CCA-C can treat northeastern species at least as 

well as CCA-C and may offer treatability advantages over 

CCA-C in species such as eastern hemlock and balsam fir. 

Two species, red maple and eastern spruce, were not adequately treated with any preservative, even after incising. 

Above-ground and ground-contact durability evaluations 

with these preservative–wood species combinations are in 

progress.
Introduction

Some tree species in the northeastern United States have relatively low commercial lumber value because of trunk size, 

growth habit, or wood properties. Increasing the value of 

these species would give forest managers more flexibility in 

economically managing the forest resource while preserving 

more traditional commercial species. Adding value to previously underutilized wood species would also create business 

and employment opportunities in rural communities. 

One option for using more northeastern species such as 

balsam fir, eastern spruce, eastern hemlock, and red maple 

in durable wood structures is pressure treatment with preservatives. Over 40 pressure-treatment facilities are already 

located in the Northeast, producing approximately 7 billion 

(7 ×109) board feet of lumber, timbers, and plywood annually (Mickelwright 1997). Before a wood species can be 

standardized for treatment with a particular preservative, 

however, it must be demonstrated that adequate penetration 

and retention can be achieved through the use of conventional pressure-treatment processes.

Research has been conducted on the treatability of northeastern species with chromated copper arsenate (CCA) and 

ammoniacal copper arsenate (ACA). Smith (1986) reported 

on the treatability of eastern white pine, eastern hemlock, 

Norway spruce, and bigtooth aspen with CCA type C 

(CCA-C). Preservative uptake was greatest in the white 

pine, but also appeared promising in incised eastern hemlock. A separate treatability study of Canadian species concluded that eastern white spruce and balsam fir were among 

the most difficult to treat with CCA-C, although incising did 

improve treatment (Richards and Inwards 1989). A subsequent study evaluated the treatability of balsam fir, eastern 

spruce, eastern hemlock, and white pine with both CCA-C 

and ACA (Gjovik and Schumann 1992). The researchers 

found that penetration was generally greater with ACA than 

CCA-C, and that the growth rate of the material (fast or 

slow) had no significant effect on penetration or retention. In 

agreement with previous researchers, Gjovik and Schumann 

found that incising significantly improved treatment. As a 

result of these studies and further unpublished efforts, eastern hemlock was added to the American Wood-Preservers’ 

Association (AWPA) Book of Standards in 1997, and the 

incising requirement for eastern white pine was modified for 

CCA-C (AWPA 1997). 

The types of preservatives used commercially have changed 

greatly since the research on treatability of northeastern 

species was conducted. Ammoniacal copper arsenate is no 

longer used in the United States, and the use of CCA-C has 

been greatly diminished. For most markets, these preservatives have been replaced with copper-based systems that do 

not contain arsenic or chromium. Arsenic-free alternatives 

that have been standardized by the AWPA include alkaline 

copper quat (ACQ), copper azole (CBA and CA-B), and 

ammoniacal copper citrate (CC). The chemistry of these 

newer wood preservatives is substantially different than that 

of CCA-C, and relatively little research has been published 

on their ability to penetrate northeastern species. A study 

evaluating CCA-C and ammoniacal copper quat (ACQ-B) 

retention (uptake) in red maple reported that uptake was 

similar in sapwood, but that uptake of CCA-C was greater in 

heartwood. Preservative penetration was not reported (Smith 

and others 1996). Since that time ACQ-B has largely been 

replaced with the amine copper formulations of ACQ (ACQ 

types C and D). We need to evaluate the ability of these new 

preservatives to penetrate into more refractory wood species and protect these wood species from decay and insect 

attack in a range of outdoor exposures. This paper describes 

research to evaluate the degree of preservative penetration 

and retention achieved in underutilized northeastern species when pressure-treated with CCA-C and arsenic-free 

alternative preservatives. An ongoing study is evaluating the 

durability of the treated wood in above-ground and groundcontact exposure.

Materials and Methods

This research was conducted through the cooperative efforts of the USDA Forest Products Laboratory (FPL); State 

& Private Forestry; Northeastern Forest Alliance; Vermont 

Department of Forest, Parks, and Recreation; preservative 

manufacturers; and cooperating lumber producers in the 

Northeast. Cooperating mills supplied eastern white pine, 

eastern spruce, balsam fir, eastern hemlock, and red maple 

lumber for the study. For comparison, the FPL obtained 

Treatability of Underutilized 

Northeastern Species with CCA 

and Alternative Wood Preservatives

Stan T. Lebow, Research Forest Products Technologist

Steven A. Halverson, Physical Science Technician

Cherilyn A. Hatfield, Statistician

Forest Products Laboratory, Madison, Wisconsin
Research Note FPL-RN-0300

2

Southern Pine lumber. Cooperating preservative manufacturers provided CCA, CC, ACQ, and CBA-A wood preservative formulations for use in the study.

Specimen Preparation

Treatability trials were conducted using standard 38- by 

89-mm (nominal 2- by 4-in.) lumber. Both incised and unincised boards were supplied for eastern spruce, balsam fir, 

eastern hemlock, and red maple species. Incised boards were 

supplied for eastern white pine only, whereas unincised 

boards were evaluated for Southern Pine only. The incising 

density was approximately 3,100 incisions/m2, with incision 

length ranging from 12 to 15 mm and incision depth ranging from 5 to 9 mm. Four end-matched specimens 203 mm 

long were cut from 15 boards of each wood species–incising 

condition combination. For the Southern Pine lumber, only 

sapwood samples were used, but the other boards contained 

a mixture of heartwood and sapwood. The four end-matched 

specimens were assigned to one of the four types of preservatives. However, the initial treatment charge with CBA-A 

solution was lost because of equipment malfunction. Those 

specimens were replaced by cutting another specimen from 

each original board. Prior to treatment, the specimens were 

conditioned in a room maintained at 23oC and 65% relative 

humidity, and then end-coated with a neoprene rubber sealant to prevent end-grain penetration. 

Preservative Formulations

The primary alternatives to CCA-C are ACQ and CBA and 

CA-B. The CCA-C was also included in this study for comparison. Ammoniacal copper citrate has not been widely 

used (and was recently withdrawn from AWPA standards) 

but was included in this study because a previous report 

(Gjovik and Schumann 1992) indicated that an ammoniacal preservative may penetrate northeastern species more 

deeply than CCA-C.

Chromated copper arsenate type C (CCA-C)

Actives composition of 47.5% CrO3, 18.5% copper 

(expressed as CuO), and 34.0% As2O5.

Alkaline copper quat type C (ACQ-C)

Actives composition of 66.7% copper (expressed as CuO) 

and 33.3% alkylbenzyldimethyl ammonium compound. The 

copper is made soluble in a solution of ethanolamine and 

water. 

Copper azole type A (CBA-A)

Actives composition of 49% Cu, 49% H3BO3, and 2% 

tebuconazole. The copper is made soluble in a solution of 

ethanolamine and water.

Ammoniacal copper citrate (CC)

Actives composition of 66.7% copper (expressed as CuO) 

and 33.3% citric acid. The copper is made soluble in a solution of ammonia and water. 

Treatment Process and Evaluation

All the treatments were conducted at room temperature. A 

treatment solution of 1% actives was used for CCA-C, CC, 

and ACQ-C, whereas a concentration of 0.74% was used for 

CBA-A. An initial vacuum of −75 kPa (25 inHg) was maintained for 30 min, the treatment solution was introduced, 

and the pressure was maintained at 1.03 MPa (150 lb/in2) 

for 2 h. The success of the treatments was evaluated by 

measuring preservative penetration and retention. Retention 

was determined by weighing each specimen before and after 

treatment to determine solution uptake and then adjusting 

for solution concentration. Penetration was determined by 

allowing the specimens to air-dry and then cutting them in 

half to expose a fresh cross section. The cross section was 

sprayed with chrome azurol–S copper indicator solution prepared in accordance with AWPA Standard C31–02 (AWPA 

2005). Penetration measurements similar to those determined commercially (by removal of increment cores) were 

obtained by measuring penetration at the midpoint of both 

narrow faces of each specimen (AWPA Standard M2–01, 

AWPA 2005). The two measurements from each specimen 

were averaged to obtain a single penetration value.

Statistical Analysis

A statistical analysis of variance was conducted on average 

preservative penetration using the SAS (SAS Institute Inc., 

Cary, North Carolina) general linear model (GLM) procedure in conjunction with a Tukey studentized range test. 

Type of preservative, wood species, and incising (incised or 

unincised) were considered as independent variables. 

Results and Discussion

Alternative preservatives generally penetrated the northeastern species at least as well as CCA-C (Table 1), and penetration by ACQ-C and CC was generally greater than that of 

CCA-C. All the alternative preservatives achieved greater 

average penetration than CCA-C in unincised Southern 

Pine, and as expected, penetration was greater in Southern 

Pine than in the northeastern species evaluated. However, 

variability was high between replicates, and the unincised 

specimens showed no significant difference in penetration 

between any of the preservatives at the 95% confidence 

level. Of the northeastern species evaluated, penetration was 

greatest in eastern white pine and least in eastern spruce. 

With incising, however, penetration of ACQ-C in eastern 

hemlock was nearly as great as that in eastern white pine. 

The benefits of incising northeastern species were reported 

in earlier studies (Gjovik and Schumann 1992; Smith 1986; 

Richards and Inwards 1989). With the exception of red 

maple, incising increased penetration in other species as 

well. The increase in penetration with incising was not always statistically significant. Significant interaction between 

wood species and incising (incised versus unincised) prevented generalizations about the relative ability of the four 

preservatives to penetrate incised specimens. Incising 
Treatability of Underutilized Northeastern Species with CCA and Alternative Wood Preservatives

3

appeared to offer the most significant increases in penetration for CC, CBA-A, and CCA, and the least improvement 

for ACQ-C. In the two most refractory species (red maple 

and eastern spruce), average penetration of the ammoniabased CC was greater than that of ACQ-C or the other preservatives, and penetration of CC was greater than CCA-C 

for all species. This agrees with earlier reports that another 

ammonia-based preservative, ACA, achieved better penetration of eastern spruce, balsam fir, and eastern hemlock than 

did CCA-C (Gjovik and Schumann 1992), and ACQ solutions containing ammonia offered improved penetration of 

some western species (Morris and others 2002). 

Minimum penetration required by AWPA standards for refractory species is typically 10 mm (AWPA 2005). In most 

cases, at least 80% of the boards sampled in a charge would 

be required to meet or exceed this minimum. In this study, 

none of the northeastern species–preservative combinations 

Table 1—Summary of penetration and retention for wood species–preservative 

combinations

Preservative Wood species Incised

 Penetration (mm) Retention (kg/m3)a

Average

Standard 

deviation Average

Standard 

deviation

CBA-Ab Balsam fir No 6 7 2.98 1.28

Balsam fir Yes 12 6 4.07 1.27

Eastern hemlock No 11 9 3.65 1.09

Eastern hemlock Yes 22 11 5.17 0.91

Eastern spruce No 3 3 1.42 1.04

Eastern spruce Yes 4 4 2.27 0.80

Red maple No 8 9 2.87 1.94

Red maple Yes 7 6 3.21 1.57

Southern Pinec No 38 8 6.09 0.27

Eastern white pine Yes 25 12 5.43 0.91

ACQ-Cd Balsam fir No 16 14 4.06 1.69

Balsam fir Yes 22 13 5.26 1.44

Eastern hemlock No 20 14 4.86 1.28

Eastern hemlock Yes 29 12 6.01 0.84

Eastern spruce No 4 5 1.63 1.02

Eastern spruce Yes 5 4 2.38 0.98

Red maple No 11 13 2.80 1.68

Red maple Yes 12 12 3.38 1.83

Southern Pine No 40 0 6.24 0.29

Eastern white pine Yes 35 10 5.94 0.77

CCA-Ce Balsam fir No 7 11 2.99 2.10

Balsam fir Yes 12 9 4.08 1.22

Eastern hemlock No 13 14 3.45 2.03

Eastern hemlock Yes 20 13 5.25 1.18

Eastern spruce No 3 4 1.49 0.98

Eastern spruce Yes 6 3 2.63 0.86

Red maple No 7 7 2.34 1.47

Red maple Yes 10 13 3.32 1.33

Southern Pine No 31 17 5.04 2.12

Eastern white pine Yes 30 11 5.54 0.81

CCf Balsam fir No 12 13 3.30 1.36

Balsam fir Yes 18 10 4.23 1.29

Eastern hemlock No 13 10 3.54 1.42

Eastern hemlock Yes 23 12 4.91 1.15

Eastern spruce No 4 3 1.39 0.68

Eastern spruce Yes 10 3 2.28 0.66

Red maple No 13 15 2.56 1.66

Red maple Yes 11 7 2.98 1.11

Southern Pine No 39 7 5.19 1.77

Eastern white pine Yes 32 11 5.02 1.06

aExpressed as acti�

 of CBA-A normalized to a 1.0% solution concentration for comparison to other preservatives.

bCopper azole type A.

cSouthern yellow pine.

dAlkaline copper quat type C.

eChromated copper arsenate type C.

f

Ammoniacal copper citrate.
4

Research Note FPL-RN-0300

met this requirement without incising (Fig. 1). Interestingly, 

the CCA-treated Southern Pine also failed this requirement 

(note that the minimum sapwood penetration of Southern 

Pine required by AWPA standards is actually 63 mm or 85% 

of the sapwood depth). After incising, penetration equaled 

or exceeded 10 mm in over 80% of the specimens for all the 

eastern hemlock treatments except CCA-C. Both ACQ-C 

and CC also met this requirement in balsam fir specimens. 

Penetration in incised eastern white pine exceeded 10 mm 

in all the specimens for all preservatives, supporting earlier 

research reporting ready treatability of this species (Gjovik 

and Schumann 1992; Smith 1986).

This research shows that relative penetration of preservatives is species-dependent. Average penetration of CC in 

incised eastern spruce was twice that of any other preservative, but CC penetration was less than that of ACQ-C in balsam fir and eastern hemlock. Average penetration of CBA-A 

was slightly greater than that of CCA-C in Southern Pine, 

but less than that of CCA-C for incised white pine. Some of 

these preservative–wood species interactions are possibly 

anomalies of this particular study, but a similar effect was 

noted in a study of the treatability of spruce–pine–fir (SPF) 

species with CCA-C and borate preservatives (Lebow and 

others 2005). In that study, lodgepole pine and Engelmann 

spruce were among the most treatable species with CCA-C 

but ranked toward the bottom in treatability with borate solutions. Balsam fir, in contrast, treated poorly with CCA-C 

but relatively well with borate solutions. 

Trends in preservative retention generally mirrored trends 

in penetration, but differences between preservatives are 

somewhat less apparent. The CC retention in incised eastern 

spruce was no greater than that of other preservatives, even 

though CC penetration appeared to be greater than for other 

preservatives. The CC retention was proportionally lower 

than penetration for other species as well. The retentions 

achieved in this study are somewhat arbitrary and reflect the 

solution concentration used. Higher retentions could have 

been achieved by increasing the solution concentration. 

Conclusions

Results indicate that the arsenic- and chromium-free alternatives to CCA-C evaluated in this study have the capacity to 

treat northeastern species at least as well as CCA-C. Some 

of the CCA-C alternatives, such as ACQ-C and CC, may 

offer advantages in improved treatment of these species. 

Eastern white pine, balsam fir, and eastern hemlock all appear to be treatable with ACQ-C, although incising may be 

necessary for eastern hemlock and balsam fir. Treatment of 

eastern spruce and red maple was not promising for any of 

the preservatives evaluated, even after incising. Treatability 

with a preservative does not necessarily ensure durability 

because fixation and microdistribution of a preservative may 

vary. Ground-contact and above-ground durability evaluations with these preservative–wood species combinations 

are in progress.

References

AWPA. 2005. Book of Standards. Selma, AL: American 

Wood Preservers’ Association.

AWPA. 1997. Standard C2. Lumber, timbers, bridge ties and 

mine ties—treatment by pressure processes. Book of Standards. Selma, AL: American Wood Preservers’ Association.

Gjovik, L.R.; Schumann, D.R. 1992. Treatability of native 

softwood species of the northeastern United States. Res. 

Pap. FPL–RP–508. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 20 p. 

Lebow, S.T.; Hatfield, C.A.; Abbott, W. 2005. Treatability 

of SPF framing lumber with CCA and borate preservatives. 

Wood and Fiber Science. 37(4): 605–614.

Mickelwright, J.T. 1998. Wood preservation statitstics 1997. 

A report to the wood preserving industry in the United 

States. Selma, AL: American Wood Preservers’ Association. 

22 pp.

Morris, P.I.; McFarling, S.M.; Zahora, A.R. 2002. Treatability of refractory species with amine and amine/

ammoniacal formulations of ACQ. Forest Products Journal. 

52(10):37–42. 

Richards, M.J.; Inwards, R.D. 1989. Treatability with CCA 

and initiation of field performance testing of refractory softwoods. In: Proceedings of the Canadian Wood Preservation 

Association. Vancouver, B.C. 10:144–178.

Smith, W.B. 1986. Treatability of several northeastern species with chromated copper arsenate wood preservative. 

Forest Products Journal. 36(7/8):63–69.

Smith, W.B.; Abdullah, N.; Herdman, D.; DeGroot, R.C. 

1996. Preservative treatment of red maple. Forest Products 

Journal. 46(3):35–41.
5

Treatability of Underutilized Northeastern Species with CCA and Alternative Wood Preservatives

1

0

10

20

30

40

50

60

70

80

90

100

Balsam fir Eastern

hemlock

Eastern

spruce

Red maple White pine

Wood species (incised)

At least 10-mm penetration (%)

0

10

20

30

40

50

60

70

80

90

100

Balsam fir Eastern

hemlock

Eastern

spruce

Red maple Southern 

yellow pine

Wood species (unincised)

CCA-C

ACQ-C

CBA-A

CC

Figure 1—Percentage of unincised (top) and incised (bottom) specimens with at least 

10-mm penetration on narrow faces (CCA-C, chromated copper arsenate type C; ACQ-C, 

alkaline copper quat type C; CBA-A, copper azole type A; CC, ammoniacal copper citrate).