Open Journal of Forestry
2013. Vol.3, No.2, 66-69
Published Online April 2013 in SciRes (http://www.scirp.org/journal/ojf) http://dx.doi.org/10.4236/ojf.2013.32011
Copyright © 2013 SciRes.
Evaluation of Durability Conferred by an Oleothermic
Treatment on Chestnut and Douglas fir through
Laboratory and in Field Tests
CNR IVALSA, Consiglio Nazionale delle Ricerche Istituto per la Valorizzazione del Legno e delle Specie
Arboree, Sesto Fiorentino, Italy
Received December 11th, 2012; revised February 11th, 2013; accepted February 27th, 2013
Copyright © 2013 Sabrina Palanti. This is an open access article distributed under the Creative Commons Attri-
bution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the
original work is properly cited.
The research evaluated two wood species, chestnut and Douglas fir, that are widespread in Tuscany,
treated with an oleothermicprocess. Efficacy of this treatment against fungal decay was assessed through
laboratory and field tests. The aim of this research was to investigate if an oleothermic process could add
value to these natural resources when utilized in Use Class 4 (EN 335) for agricultural purposes such as
vineyard poles. The treatment was effective on sapwood of both wood species in laboratory test, giving a
protection similar to the untreated heartwood but in case of chestnut, it was easily washed away. In field
test the leaching during the outdoor exposure reduced the resistance to fungal decay in both species.
Keywords: Conferred Durability; Chestnut; Douglas fir; Oleothermic Treatment
The conventional wood protection for Use Classes 3 and 4
according to EN 335 (2006) is actually based on broad spectrum
biocide formulations such as copper/organic biocides, copper-
organometallics, metal free preservatives (Hughes 2004), and
alkyl ammonium compounds (Pernak et al. 2004).
In the last decade, there has been a great interest within Eu-
rope in oils and water repellents for wood preservation prince-
pally focusing on screening of natural and synthetic oils (Sailer
and Rapp 2001; Van Eckeveld et al. 2001; Palanti et al. 2004),
and on the processes for development of wood preservation
technology (Thevenon 2001; Treu et al. 2001). Chestnut and
Douglas fir are widely planted in Tuscany. Tuscany forest con-
tains 862 hectares with 21% of chestnut and 4% conifers prin-
cipally pine, Douglas fir and silver fir (Sanchez et al. 2005).
Promoting the use of these species for agricultural purpose
could add value to this natural resource.
Oleothermic treatment was explored for improving the natu-
ral durability of these species (Grenier et al. 2003). This process
has been known as eco-friendly, biocide-free, cheaper, capable
of being applied without drying the wood.
Oleothermic treatment also prevented the tannin leaching
from chestnut which could maintain natural durability for a
longer period (Grenier et al. 2003). While these results are pro-
mising, there is few data on the long-term performance of oleo-
thermic treated chestnut and Douglas fir heartwood and sap-
wood. In order to evaluate these materials the following test
1) Laboratory tests of chestnut and Douglas fir sapwood,
treated with oleothermic treatment, in according to EN 113 and
2) Natural durability test in according to EN 252 (in field) of
Chestnut and Douglas fir.
3) Resistance test in according to EN 252 of treated Chestnut
and Douglas fir.
Materials and Methods
The tested wood species were chestnut (Castanea sativa Mill.)
and Douglas fir (Pseudotsugamenziesii Mirb. Franco) of Tus-
can origin, from Casentino, a valley near Arezzo. The reference
controls were Scots pine (Pinus sylvestris L.) and European
beech (Fagus sylvatica L.), sapwood, in accordance with Euro-
pean norms EN 350-1:1996 and EN 113:1996 and EN 252:
The oleothermic treatment was performed at CIRAD in
Montpellier, France using a two-step process (Grenier et al.
Chestnut and Douglas fir planks were conditioned at 20˚C
and 65% RH, cut in samples and sent to the plant for oleother-
The treated samples were then conditioned to constant
weight at 20˚C and 65% RH.
Wood blocks (50 ± 0.5) × (25 ± 0.5) × (15 ± 0.5) mm3, were
cut from the boards.
Natural durability and the durability conferred by oil treat-
ment of chestnut and Douglas fir were assessed in accordance
with European standards EN 113 and EN 350. A comparison of
resistance against fungi before and after leaching in accordance
with EN 84 was carried out.
The fungi utilized for chestnut and Douglas fir were two
brown rots, Coniophora puteana (Schumacher ex Fries) Kar-
sten, strain BAM Ebw. 15 and Gloeophyllum trabeum (Persoon
ex Fries) Murril, strain BAM Ebw. 19. The white rot fungus,
Coriolus versicolor (Linnaeus) Quélet, strain CTB 863 A was
only utilized for chestnut. The brown rot fungus Poria placenta
(Fries Cooke) sensu J. Eriksson, strain FPRL280 was utilized
for Douglas fir. These fungire present the certificated ones util-
ized in the European normative.
The wood samples were exposed to fungal attack for 16
weeks in a conditioning room (22˚C ± 2˚C, 70% ± 5% RH). For
each set, a treated sample was placed with a reference untreated
sample in a Kolle flask containing one of the test fungi growing
on 20 ml of 4% malt and 2.5% agar medium. Another set of
five untreated wood specimens was used to check for strain
virulence for each tested fungus.
The resistance against fungi was evaluated using mass loss of
wood, which was calculated for each individual block as the
difference between the dry mass before and after the fungal
exposure. The minimum of mass loss on reference wood blocks
were 30% for C. puteana and 20% for P. placenta, G. trabeum
and T. versicolor.
The natural durability class was calculated according to
CEN/TS 15083, expressed as durability class, against wood
destroying basidiomycetes fungi based on the higher median
mass loss determined for all test specimens exposed to each of
the three test fungi. Using the following scale: 1- very durable
(mass loss ≤ 5%), 2- durable (mass loss >5% to ≤10%), 3-
moderately durable (mass loss >10% to ≤15%) 4- slightly du-
rable (mass loss >15% to ≤30%), 5- not durable (mass loss >
Leaching in Accordance with EN 84
Wood samples, see Table 1, were subjected to leaching ac-
cording to EN 84: 1996. The cycle consisted of an initial 4 kPa
vacuum - atmospheric pressure cycle with deionized water EN
ISO 3696 (1996). The wood specimens were maintained in
water (ratio of water to wood 5:1) for 14 days with 9 water
changes, and then conditioned to constant mass before being
exposed to one of the test fungus.
Median mass losses % of non-treated Chestnut heartwood or sapwood
that was oleotheric treated. Samples were exposed to 3 fungi of EN
113 (H: heartwood, S: sapwood, T: Treated, L: leached, Y: yes, N:not,
D class: durability class ).
Median mass loss %
(n = 5)
S Y N 1.24 1.49 - 1
S Y Y 12.91 12.50 12.92 3
H N N 1.33 1.17 0.92 1
H N Y 3.41 3.39 3.10 1
In Field Test
In ground performance tests were performed in accordance
with EN 252: 1989 over a 70 months period (July 2005 to April
2011). The test site was on an agricultural soil situated in Tus-
cany, Cesa, Val di Chiana Arezzo.
Fifteen stakes for wood species, dimensions (500 ± 1) × (50
± 3) × (25 ± 0.3) mm3, derived from heartwood chestnut, heart-
wood and sapwood Douglas fir were conditioned and cut be-
fore being sent to the plant for oleothermic treatment.
The treated stakes were placed vertically in the soil leaving
half of length exposed.
Untreated stakes of Scots pine and beech were also buried up
to half their length in the soil test site as reference controls.
Fungal decay was annually evaluated in the area around the
ground contact. Inspections were carried out by giving a light
blow to the upper part of each stake to determine if the stake
was close to failure, followed by removal from the ground.
Surface examination was probed with an awl to detect weak-
ness due to fungal rot. Fungal decay was evaluated on the basis
of the depth of fungal softening and damaged area according to
a specific rating system: 0 sound, 1 slight attack, 2 moderate
attack, 3 severe attack and 4 failure (stake breaks in the ground
after blowing). The evaluation was performed in accordance
with guideline for EN 252 of the Nordic Wood Preservation
Council (Borsholt and Henriksen, 1992).
It is possible to calculate the mean life as indicated in stan-
dard EN 350-1 when all stakes fail. The mean life, where not all
stakes have reached the end of their life, can be predicted using
the procedure of Purslow, 1976.
The number of replicates utilized for calculating average de-
cay grade was unequal for wood species and treatments because
some stakes failed as the test site who maintained and it was not
possible to determine whether decay was the sole cause of failure.
Analysis of variance (ANOVA) one-way, ANOVA multiple
factors way and a post-hoc Tukey HSD multiple comparisons
of means were carried out with open source R software.
The statistical analyses were on the following tests:
Laboratory test: chestnut and Douglas fir mass loss % of
blocks exposed to C. puteana.
Field test: chestnut decay rating after six year; Douglas stakes
rating of third (mid-term evaluation) and sixth year.
Results and Discussion
Average uptake of oleothermic treatment on sapwood (n = 39)
was 13% as (m/m) %.
The results obtained by natural and the conferred durability
are reported in Table 1. Results due G. trabeum were omitted
because the beech reference wood blocks had mass losses lower
than minimum required by the standard.
The oleothermic treatment provided a good protection to
sapwood but it was not fixed very well. Durability rating de-
creased from 1 to 3 when the wood was leached in accordance
with ageing procedure EN 84. Durability of non-leached treated
was similar to the inherent durability of non-leached heartwood.
Weight losses of non-treated heartwood samples increasedwith
Copyright © 2013 SciRes. 67
leaching procedure, but the increase did not affect the durability
The one-way analysis of variance (Anova) of mass loss % of
different treatment against C. puteana, indicated that there were
significant differences between samples (F3,16 = 2.2e−16***).
The post hoc Tukey multiple comparisons of means, at a 95%
family-wise confidence level, showed a significant difference in
leached and non-leached treated chestnut underlined that the
oleothermic gave a good durability (Table 2). In leached and
non-leached heartwood the significant difference depended on
leaching procedure that washed away the natural extractives. It
was also interesting observe that only pair with not significant
difference was untreated heartwood and treated sapwood where
it was found a similar grade of effectiveness when exposed to C.
puteana. This fact confirmed that sapwood treated with oleo-
thermic treatment reached the same grade of durability of the
The average oleothermic uptake (n = 4) in sapwood and
heartwood were 16% and 14% m/m % respectively.
The oleothermic treatment gave a good protection to Douglas
fir sapwood, improving durability to class 2 (Table 3) in both
leached and non-leached blocks.
In the untreated Douglas fir heartwood the leaching proce-
dure determined a decreasing in durability from class 2 to 4.
Probably this low durability was due to the fact that the leach-
ing procedure washed away most part of the extractives.
Post hoc Tukey multiple comparisons of means at a 95% family-wise
confidence level. T: treated, U untreated, L Leached, S sapwood, H
p value at
TSL-TS 11.692 10.7594919 12.624508 0.0000000
UH-TS 0.116 −0.8165081 1.048508 0.9839834
UHL-TS 2.396 1.463491 3.328508 0.0000089
UH-TSL −11.576 −12.5085081 −10.643492 0.0000000
UHL-TL −9.296 −10.2285081 −8.363492 0.0000000
UHL-UH 2.280 1.3474919 3.212508 0.0000164
Median mass loss % of Douglas fir (H: heartwood, S: sapwood, T:
Treated, L: leached, Y: yes, N:not). In the brackets the number of
samples utilized for the determination of the medians are reported.D
class: Durability class.
Median Mass loss %
S Y N 1.37 (2) - 7.67 (2) 2
S Y Y 7.42 (5) 3.62 (3) 5.91 (4) 2
H N N 3.88 (3) 3.79 (2) 9.03 (4) 2
H N Y 12.37 (3) 1.45 (4) 19.67 (2) 4
S N N 11.26 (4) 5.02 (2) 13.89 (4) 3
The set of untreated sapwood gave reaching the durability
class 3 (Table 2).
The one-way analysis of variance (Anova) of mass loss
showed that there were significant difference among treatments
with fungus C. puteana, gave significant differences between
means ((F6,16 = 0.784800**). The post hoc Tukey multiple
comparisons of means, 95% family-wise confidence level, evi-
denced significance in the mass loss in all combination with the
exclusion of the pairs untreated heartwood-treated and leached
sapwood, untreated heartwood-treated sapwood. The efficacy
of treatment when applied into sapwood, and its fixation is
evidenced by not significance between untreated heartwood-
treated and leached sapwood.
In Field Test
The year-by-year results obtained by in field test of chestnut
are reported in Table 4.
Only a slight difference was observed between treated and
non-treated chestnut stakes. Four of eight treated stakes failed
(decay grade 4) at the end of the test, and the mean life of these
stakes was six years. Five of twelve untreated chestnut failed at
sixth year with a mean life of 6 years, the number of ruptures
was 6 on 12 and the mean life was, as well as treated ones, six
years. The beech control stakes all failed after two years.
The analysis of variance of the decay grade of 68 months
evidenced significant difference between treated and non-
treated samples (F2,27 = 0.03873*). The post hoc Tukey multi-
ple comparisons of means at 95% family-wise confidence level,
indicated that there are significant differences in decay grade
were weather untreated chestnut and beech.
In the Table 5 are reported the overall results obtained from
Douglas fir stakes.
In the treated heartwood, at the end of the test, six stakes on
eight reached the rupture with a mean life 5.33 years. In the
treated Douglas fir sapwood set at the end of the test 9 on 10
stakes reached the decay grade 4 with a mean life 5.11 years.
The Douglas fir untreated set sapwood reached a mean life 4.60
years. In the untreated heartwood set only two stakes on 10
reached the rupture.
The decay grade of 68 months evidenced significance be-
tween samples (F4,38 = 0.00064***) and the post hoc Tukey
multiple comparisons of means, 95% family-wise confi-
dencelevel, gave as significant the pairs untreated Douglas fir
Decay rating of average annual evaluations of Chestnut in field testing.
Average decay rati ng
13 0.23 0.21 2.1
23 0.25 1.00 3.6
36 1.13 1.57 3.9
47 1.75 2.21 4.0
62 2.25 2.50 Failed
68 3.38 3.29 Failed
Copyright © 2013 SciRes.
Copyright © 2013 SciRes. 69
Decay rating of field average annual evaluations of Douglas fir.
Average decay rati ng
time (m on th ) Trea ted Douglas fir
sapwood Treated Douglas fir
heartwood Untreated Douglas fir
sapwood Untreated Douglas fir
heartwood Scot pine sapwood
13 1.09 0.11 1.00 0.30 0.3
23 1.36 0.78 1.29 1.00 1.1
36 1.55 1.44 2.29 1.70 4
47 2.80 2.63 3.14 2.20 4
62 2.90 2.63 3.14 2.40 Failed
68 3.89 3.75 3.71 3.11 Failed
heart wood-treated Douglas fir sapwood, untreated Douglas fir
heartwood-treated Douglas fir heartwood and Scot pine-un-
treated Douglas fir heartwood.
The results showed that oleothermic treatment improved the
durability of chestnut and Douglas fir, both laboratory and
fields exposition. Oleothermic treatment provided a good pro-
tection to chestnut sapwood as evidenced by laboratory ex-
periments, but the treatment it was susceptible to the leaching
during the field test.
With regarding Douglas fir field test is remarkable that the
significant difference observed in the pair heartwood treated
and not treated was due also to the presence of natural extrac-
tives inside the wood, responsible for the conferred durability.
The protection given by oil was susceptible to leach and further
studies are recommended to develop methods for fixing the
The author thanks the Regional Agency for Agriculture De-
veloping and Innovation (ARSIA) that supported this research,
CIRAD for theoleothermic treatment, and Mrs. Anna Maria
Torniai from CNR Trees and Timber Institute who helped with
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