Testing of Wood Finishes for Durability - July 2005
In the bed wood finish test series last summer we evaluated products widely advertised and
available in paint stores or home improvement stores. We applied them in a standard way
either brushing or spraying 2 or 3 coats, according to the instructions with each product.
Some of the coatings were applied over a linseed oil seal to improve their durability.
All the coatings tested showed failure in less than 6 months, most in less than 2 months of
continuous exposure to the weather. While continuous exposure is more severe than most
custom or classic trucks would experience, we are hoping to find a finish that will last longer
to satisfy the needs of most truck owners.
For this second round of tests, we are using more exotic coatings such as would be used in
marine applications or exterior architectural coatings. Since the coatings that were
applied over a seal coat seemed to last longer in the first tests, we are using that technique
in different combinations for several of the test coatings in this second round of tests.
We are also including some testing of finishes on Pine boards. The clear coatings include
two types of clear marine epoxy, Pelucid by POR 15, Glisten by POR 15, Aliphatic Urethane,
Minwax Helmsman, and Automotive clear coat. We will also be including Minwax Helmsman
varnish applied on boards that have been sealed with linseed oil. Clear coatings for
exterior use such as Minwax Helmsman have ultraviolet absorbers which protect the coating and
the wood substrate from damage caused by ultraviolet from the sun. With long term exposure
to the sun, ultraviolet absorbers will eventually deteriorate and allow the harmful ultraviolet
rays to penetrate to the wood below. That is why even top quality clear coatings need to
be sanded and re-applied when they are exposed to the sunlight for extended times. We
expect the combinations used in these tests will result in finishes more durable than those in
the first tests and hopefully these test results will help you decide if such a finish is worth
the time and expense for your application.
As before, we are testing 10 finish systems with 3 boards being coated with each system for
a total of 30 boards. Each board is about 5" X 24", red oak or yellow pine, sanded and
machined as we do for all our bedwood products. All the boards are attached in the test
fixture and held in place with Mar-K type 430 unpolished stainless bed strips and
polished stainless bolts. The boards are coated on all surfaces, with the ends being
coated as much as they will absorb. Sharp edges of the boards are all sanded to a slight
radius to reduce the tendency of coatings to thin at sharp edges. The specific method of
application for each coating is different and is described in detail below. The test
fixture is positioned outdoors on the northwest side of our manufacturing plant and will be
exposed to weather continuously until the coatings fail.
The rules of the test are simple. We coated the boards with each product according to
the supplier's instructions and allowed them to cure as recommended before exposing them to the
elements. Our intention is to leave the samples outdoors continuously exposed to the
Oklahoma weather until all coatings have failed. Results and observations will be
reported and posted during the test.
Products and Procedures
We purchased all these coatings and products from suppliers just as a typical consumer would
do and used our best judgment and experience along with the manufacturers' recommendations in
deciding on the application method. We do not currently sell any of these products and have
no affiliation with the companies or products involved. Our purpose in these tests is to
help our customers decide what coating system may best meet their needs. Because of the
many variables in the materials, application methods, and environmental conditions, these results
may not be the same as you will experience. Use them only as a comparative guide. We
recommend that you perform your own evaluation of the finish that you select before coating your
complete bed wood set, especially if your truck will be exposed to the sunlight and weather.
Begin your tests early in your restoration process so you will have your own results when you are
ready to finish your bed wood. MAR-K can provide small pieces of Oak or Pine bedwood for your
We have selected two epoxy products to include in these tests. In general epoxy is a
two-component coating and is very strong and tough. It adheres well to wood and is resistant
to water. Epoxy is not resistant to ultraviolet rays and is readily degraded by sunlight,
which is why epoxy is not used as a clear finish topcoat. We used the epoxy as a "primer"
and coated it with a clear finish that is resistant to the sunlight, thereby gaining the
durability and adhesion to the wood provided by the epoxy and combining it with a clear finish
coat that is resistant to the sunlight. These tests will evaluate the effectiveness of this
type of coating system.
CPES by Smith & Co
The epoxy called CPES (clear penetrating epoxy sealer) was purchased from Smith & Co.
It is applied by saturating the wood boards with the epoxy as much as possible then applying the top
coating when the epoxy is dry to touch but roughly half-cured, about 1-1/2 days later.
According to the CPES instructions this will cause "the second material to cure first and the resin
film of the CPES to cure last, gluing down the second material."... "The CPES glues down the varnish
and the ultraviolet absorbers in the varnish protect the epoxy and the wood from degradation by
sunlight." We used automotive clear coat paint and aliphatic urethane as topcoats over CPES in
these tests. By applying multiple coats and block sanding between coats of the topcoats, we
were able to obtain an acceptable smooth glossy finish. This finish product is being used on both
pine and oak for this test.
RAKA 350 epoxy with RAKA 127 hardener by RAKA Inc.
The second epoxy tested was supplied by RAKA INC. This supplier recommended applying several
coats of the epoxy with 12 hours between coats and then allowing the epoxy to fully cure for at least
a week before applying secondary topcoats such as varnish. We allowed over a month to cure,
then the epoxy was block sanded to obtain a smooth surface and to provide a mechanical bond between
the epoxy and the topcoat. We used Minwax Helmsman and automotive clear coat as topcoat finishes
for the RAKA epoxy. This initially resulted in a deep looking glass-smooth finish and is quite
PELUCID by POR-15 and HELMSMAN by Minwax
Pelucid is a single component polyurethane clear coating. In the first series of tests last
year, we tested Pelucid by itself and found it to be quite durable. As noted, however, it is
not intended for continuous outdoor exposure. Although adhesion was good, the sun darkened the
wood significantly and some small cracks in the finish occurred. For this second test, we used
the Pelucid as a primer coat to seal the wood and provide adhesion and used Minwax Helmsman Spar
Urethane for a finish coat to provide UV protectioin. We applied three coats of Pelucid a few
hours apart then allowed it to cure 4 days. When cured the Pelucid was block sanded and then
three coats of Minwax Helmsman Spar Urethane were applied. This system is being tested on
both pine and oak.
GLISTEN PC by POR-15
Glisten PC is a two component high gloss clear top coat designed for wood surfaces.
It has UV protection and is intended for exterior use. It is also resistant to many chemicals
so it would appear to be well suited for pickup bed applications. We applied one full coat and
allowed it to cure 24 hours before sanding and applying 3 more coats. No additional top coat
is needed since Glisten is resistant to the sunlight and is designed to be a topcoat.
POR-15 Black Rust Preventative Paint and BEHR Gloss Black exterior paint
POR-15 Rust Preventative Paint dries to a very hard waterproof finish but it is UV sensitive.
We applied three coats of black POR-15 Rust Preventative Paint paint to the boards and topcoated with
the same BEHR gloss black paint that was used in the first test series. The POR-15 Rust
Preventative Paint will provide the strength and adhesion and the BEHR gloss black will provide the
resistance to sunlight.
These procedures and coatings are only some samples of the many types of finishes available.
This is an accelerated test because of the continuous exposure and failures probably will occur sooner
than would be expected on a typical custom bedwood application. Most customers would not park
their custom vehicle unprotected in the sun and rain during the heat of the summer. The finished
bed wood should be considered like a piece of furniture and not neglected. One must remember
that wood is not a stable material like steel and is continuously changing and deteriorating.
Because of varying environmental conditions, wood is always in the process of either drying out or
gaining moisture, as well as being attacked by the ultraviolet rays of sunlight. It is only as
durable as the finish that is applied and maintained. Here are some other suggestions and
helpful bits of information.
- Always do experimenting with the finish selected to see how it responds to your application
method. The experiments should be done on scrap wood that is the same as the bedwood, but
not on the bed wood. Do not apply second and third coats too soon or too late. There
is an optimum "time window" in which the adhesion between coats will be the best and it is
different for each kind of finish.
- Exposure of bare wood to sunlight will discolor the wood and will also reduce the adhesion of
the coating due to deterioration of the wood surface. Coat the wood as soon as is
practical and do not store it where it is exposed to sunlight.
- Sand a radius on all sharp edges to improve coating thickness at the edges. Our testing
has shown the most failures at the edges of the boards, probably due to thinning of the coating
at those points.
- Moisture and sunlight (ultraviolet rays) are what cause the wood and finishes to fail,
especially when both are present. Protect your finished bed wood from both.
- If you must drill holes in the wood after it is finished, be sure to smooth the edges of the
holes and coat the inside of the holes with the finishing material.
- After the wood is installed, frequently check the wood finish for signs of failure.
Usually these will first occur at the sharp edges or as a hairline split beginning at one end
of the board. As the tests show, these failures can occur in as little as one month,
depending on conditions, and they will not heal themselves. All problems should be repaired
right away to maintain the long life of the finish. You cannot "paint it and forget it"
like a finish on metal parts.
- In general, pigmented premium paint will provide longer lasting protection from sunlight damage
than clear finishes. Also, gloss paints generally have more resistance to sunlight damage
than semi-gloss or flat finishes.
Bed Wood Finish Test Update, November 1, 2005
The second test group has been in place for over three months. There is not much to report
because none of the test finishes have had any failure at this time. All look great and we
believe some of these finishes could be very durable and long lasting. Because there has been
no degradation or failure, it is not possible to predict which would likely be the best.
The second test series is intended to evaluate the benefit of using more durable and difficult
finishing methods, including epoxies, two part urethanes and clear coats. The use of these
finishing systems is time consuming and requires close attention to detail. Hopefully the
benefit is worth it. A couple items to keep in mind when comparing the current tests to the
- The first test started a little earlier in the summer of 2004 and saw more severe summer
weather extremes than the second test
- Most of the finishes in the first test had shown at least some indication of failure by the
two-month time period. This is probably due to the severity of the weather in summer 2004
and to the use of simpler less effective coating systems in the first tests.
Bed Wood Finish Test Update, November 21, 2005
The wood finish test continues at Mar-K. We appreciate all the questions and suggestions
you have written and the interest shown. Hopefully these tests will help you make educated choices
regarding your bed wood finish. At this date, all the finishes except one have shown no
indication of failure.
The GLISTEN product by POR15 is showing failure peeling or separation after 4 months of
continuous exposure to the weather. This failure was first noted about November 15th.
The weather during this test has ranged from 100 degree summer weather in the direct sun to mid
twenty's late fall cold weather and it has been unusually dry with little rain and no snow to
date. GLISTEN is the only finish system in this test that does not consist of a sealer or
penetrating prime coat followed by a topcoat of some kind. Glisten is promoted by POR15 to
be suitable for exterior use and no prime coat is suggested. All other products in the
current test are doing very well with no noticeable discoloration or peeling.
The photo shows the areas of failure. There are several places along the edges of the
boards next to the bed strips that are beginning to separate as indicated by the white translucent
spots. You can see the failure is not isolated but is evident on several of the GLISTEN
coated boards. It is not evident whether or not the peeling is between coats of the GLISTEN
or separation of all the coats from the wood itself. If this were in your truck bed, you
would probably just sand it and recoat the damaged areas to get some more life out of the coating
since the center areas of the boards appears to be still intact. We will allow the coating
to continue in the test without repairing it at this time.
A few general comments about GLISTEN. It made a very hard glossy surface that was quite
attractive. It is a two component product that you mix and apply somewhat like automotive
clearcoats. It sprays on smooth and it is not necessary to buff the GLISTEN to make it
shiny. GLISTEN was probably the easiest of the finishes in this test to apply and it may
make a satisfactory finish if your truck is not often exposed to the weather. Needed repairs
could be easily made by sanding the damage areas and using a touchup gun to spray on a few more
coats. It is available in small quantities from POR15 and we suggest you do testing in your
own environment before committing to this coating.
Wood finishes are usually weakest at the edges of boards since coatings naturally are thinner
at a sharp edge. All the boards in the test including these three that failed were sanded
before coating and all the sharp edges were 'eased' by sanding them to a slight radius. The
failure may have been delayed if the boards had been sanded to an even more rounded edge before
they were coated. This would have allowed the GLISTEN to be a little thicker on the edges
and possibly prolonged the life of this coating. No matter what coating you use, it will
probably give longer life if you round all the edges significantly to help prevent this weak area.
Bed Wood Finish Test Update, December 31, 2005
There is no visible deterioration of the finishes since the last update. The test has
been in place since July 2005, continuously exposed to the Oklahoma weather. The boards
have been washed and cleaned periodically, but have not been waxed or protected from the
weather. This update will be more of a general description of the appearances of the
finishes and how well they are doing from a purely cosmetic view.
- CPES epoxy with aliphatic urethane topcoat. This is an oak sample and it is coated
with one heavy coat of the CPES epoxy and then topcoated with Aliphatic urethane after the
epoxy had cured about 36 hours. Three coats of Aliphatic were sprayed, without
sanding between coats.
- This coating has darkened slightly, probably from UV exposure.
- The coating is not glass smooth but is still shiny and is attractive.
- The boards are fully sealed and there are no visible defects.
- CPES epoxy with Minwax Helmsman Spar Urethane topcoat. This is a pine sample and
it is coated with one heavy coat of the CPES epoxy and then topcoated with three coats of
Helmsman after the epoxy had cured about 48 hours. Helmsman was scuff sanded between
- The coating has darkened slightly but is still very attractive.
- The boards are still well sealed and no flaws in the coating are visible.
- RAKA epoxy with automotive clear topcoat. This is an oak sample. Two coats
of the RAKA epoxy were applied and allowed to fully cure more than 7 days. Then the
epoxy was block sanded smooth before spraying 3 coats of PPG clearcoat. The clear
was not sanded or buffed.
- This coating is water clear and has not darkened.
- The oak still looks pink, practically matching the color of unfinished red oak.
If you want a traditional amber color oak wood, this finish may not work for you.
- The finish is glass smooth with no noticeable texture or orange peel.
- The boards are sealed well and there are no visible flaws
- CPES epoxy with automotive clear topcoat. This is an oak sample. One heavy
saturating coat of CPES epoxy was applied then topcoated with 3 coats of PPG clearcoat after
the epoxy had cured about 36 hours.
- The coating is a very light color, darkening only slightly.
- The finish is not as smooth as the #3 sample probably because the CPES was not
- An attractive finish, still very glossy surface.
- The edge of one board may be showing a failure, possibly from insufficient coating
thickness. The other boards and surfaces are sealed and showing no flaws.
We will watch this one.
- RAKA epoxy with Minwax Helmsman Spar Urethane topcoat. This is an oak sample. Two
coats of RAKA epoxy were applied and allowed to fully cure more than 7 days. Then the
epoxy was block sanded smooth before spraying 3 coats of Helmsman, scuff sanded between coats.
- The wood has an amber color, typical of the Helmsman coating.
- The surface is smooth and glossy.
- The edge of one board may be showing a failure, possibly from insufficient coating
thickness. The other boards and surfaces are sealed and showing no flaws. We will
watch this one.
- Pelucid primer coat with Minwax Helmsman Spar Urethane topcoat. This is an oak sample.
Three coats of Pelucid applied 3 hours apart, then allowed to cure for four days. After block
sanding, 3 more coats of Helmsman were applied, scuff sanded between coats
- The coating has darkened the wood slightly.
- No flaws are visible and the boards are fully sealed.
- POR-15 Rust Preventative Paint with Behr black glossy enamel. Three coats of POR-15 Rust
Preventative Paint applied 3 hours apart and the first coat of Behr applied 3 hours after the last
coat of POR-15 Rust Preventative Paint. Two more coats of Behr applied the next day.
- This appears to be a durable black paint system.
- Possible slight reduction of gloss since the initial application in July.
- You can see the grain pattern of the wood but the boards are fully sealed and there are
no flaws in the coating.
- Glisten, primer and topcoat. This is an oak sample. One coat of Glisten was applied
and allowed to cure 24 hours. It was then scuff sanded and three more coats of Glisten were
applied, 1 hour between coats.
- There is more orange peel than the other samples, but it is shiny.
- Failure of this coating is appearing as noted in previous update (see above).
- Pelucid primer coat with Minwax Helmsman Spar Urethane topcoat. This is a pine sample.
Three coats of Pelucid applied 3 hours apart, then allowed to cure for four days. After block
sanding, 3 more coats of Helmsman were applied, scuff sanded between coats
- The coating has darkened the wood slightly, it is a natural looking amber color.
- No flaws are visible and the boards are fully sealed.
- Linseed oil seal with Minwax Helmsman topcoat. This is an oak sample. The boards were
saturated with hot (about 120 degree) linseed oil and allowed to cure for 3 months. Boards
were wiped with turpentine to remove excess dried linseed oil, then three coats of Helmsman were
applied, scuff sanding between coats.
- The oak is darkened, probably both by the sun and by the linseed oil.
- The surface is not as glass smooth as some of the others, but quite acceptable.
- There are no defects in the finish, the boards are fully sealed
It should be noted that this has been an unusually dry fall season and the samples have seen less
than average rain and snow. Still, there seems little doubt these current finishes being tested
are superior to the finishes of the first test. The two stage coatings system combines the
benefit of a strong primer coat with the UV resistance of a good top coat. We will continue to
monitor the finishes and bring updates as information is available.
Bed Wood Finish Test Update, April 10, 2006
This is a brief update of the Mar-K wood finish test series, an on-going comparison of ten
different bed wood finishing procedures. This test has been in continuous exposure to the
weather since August of 2005.
We noted in a previous update that the Glisten product, sample number 8, was failing. It is
peeling away at the edges of several boards. This condition has worsened as shown in the photo.
A second possible failure was noted earlier and that coating area of failure has enlarged
slightly. It is sample number 5, a combination of RAKA epoxy seal coat and a top coat of
Helmsman Spar Urethane. This failure appeared only on one board of the three, but it has
gradually enlarged to the size shown in the photo. The RAKA epoxy still is protecting the
wood, but epoxy needs a top coat of UV resistant product for long lasting service, so without
repair, this coating will eventually fail. Since it is occurring on only one board of the
three, it is possible that the failure is the result of improper application of the Helmsman in
that spot, or from contamination of the surface before it was recoated with the Helmsman.
We will continue to monitor this coating closely, and provide updates as appropriate.
Sample number 10, a linseed oil seal coat with a Helmsman Spar Urethane topcoat, is now showing a
small area of separation, see the photo. The wood is still protected under the varnish by
the linseed oil but it will deteriorate soon without the urethane topcoat protection.
Sample number 3 is now showing a discoloration in a few spots, which is typical of the failures we
have seen. This finish is RAKA epoxy with automotive clearcoat top coat. The failure
is just beginning to show. We will provide more information in future updates as this finish
continues to deteriorate.
So far, four wood finish systems have failed, all by having a topcoat separate from the sealing
coat in a relatively small area of the board. Also we note that all the boards first showed
failure at the edge of the board near the bed strip groove. When we were coating the boards
we were careful to have a very generous coating thickness on the ends of the boards, as that area
is often the place where failures begin. We have no failures at the end grain areas of the
boards in this test. These coating systems are all significantly better than the coatings of
our first series of tests.
Bed Wood Finish Test Update, August 20, 2006
The current test series for bed wood finishes continues. It has been approximately one
year since we placed the ten wood finish samples outdoors in the Oklahoma weather. They
have been continuously exposed to whatever Mother Nature has offered since July of 2005. All
of the samples currently tested have much greater durability than the finishes tested in summer of
2004. It appears that finish systems which include an effective seal coat followed by protective
coats of high quality exterior paint or urethane varnish will provide a long lasting bed wood
finish. This is of course a very unscientific test and your results may be different than
ours. Note that this Oklahoma summer has seen record heat with many days over 100 degrees and
very little rain or moisture. Also remember that this is a somewhat accelerated test since
trucks with custom bed wood are usually protected much better than our test samples and would not be
left outdoors 24/7 in all kinds of weather. The finish on your bed would probably last longer
than one year, but remember that all wood finishes need to be refreshed occasionally, depending on
the use or the amount of exposure to the elements.
While many of the test sample finishes have failed at least to some degree, only the Glisten
(sample #8) and the Helmsman over linseed oil (sample #10) have failed to the point that it would be
impractical to repair. Based on these tests, the Glisten and linseed oil systems would not be
recommended for bed wood applications.
The Glisten failed by separating from the wood in a few months as reported in our first update.
After several months of continued exposure, it has large areas of separation, pretty typical of what
we have seen from finishes that do not have a primer or seal coat. See picture left.
The Helmsman Spar Urethane over the linseed oil sealer began to show separation between the Helmsman
and the linseed oil seal coat in the spring of 2006. This was first reported in April 2006.
Since that time the area of failure has enlarged and now extends several inches along the edge of the
board. See picture left. The separation is more difficult to see since the linseed oil
remains to protect the bare wood, although it does not offer the full protection of the original
coatings. While this sample could be repaired it would probably require removing the complete
coating of Helmsman and recoating. We do not plan to repair the finish for this test.
Several of the remaining sample coatings have some small failure areas. Only the black painted
oak sample with the POR-15 primer and the pine with CPES primer and Helmsman topcoat are showing no
sign of failure.
The numbered finishes and their failures are described as follows.
- CPES epoxy primer by Smith & Company is the seal
coat with aliphatic urethane
topcoat. This finish system on the oak sample has performed very well. There is a hairline
crack beginning to show in one of the boards and the end is split in another. All three boards
have darkened noticeably. The darkening may indicate the aliphatic urethane has lost some of its
UV absorption capability and should be renewed. This system would probably be a very good method
of finishing bed wood, and periodic refinishing would be acceptable.
- CPES epoxy primer by Smith & Company is the seal coat with three coats of Minwax Helmsman
topcoat. This finish system is on a pine sample and there are no defects showing. The ends
do not seem as well sealed as the pine with Pelucid (sample #9) but no splits or separation has
occurred. The wood has darkened noticeably but is still very attractive and well sealed.
This finish system is recommended for pine boards that will have a natural finish. We would
recommend adding extra seal coats of epoxy on the ends of the boards to provide a better seal.
- Two coats of RAKA epoxy as a primer and three coats of automotive
clear coat as a topcoat. This finish system is on an oak sample and it has several small failure
areas on the surface but none on the ends of the boards. There is very little darkening of the
wood. This sample finish was glass smooth because the epoxy was allowed to fully cure and it was
block sanded before applying the automotive clear. The finish did not darken the wood at all,
since the automotive clearcoat goes on water clear. Although it has held up fairly well, the
finish would not be considered as attractive to most people who would want a more
"furniture" like appearance.
- CPES epoxy primer by Smith & Company is the seal coat with three coats of automotive clear sprayed
for a topcoat. This finish system is on an oak sample and it also has some small failure areas.
It has very little darkening of the wood. The finish initially was smooth but not quite as smooth as
the #3 sample since the CPES was not block sanded before applying the topcoat. The appearance is much the
same as RAKA #3 except the ends of the boards have some splits. If this system is used on oak, some
more experimentation should be done to penetrate the ends better with the epoxy before applying the topcoat.
- Two coats of RAKA epoxy as a primer and three coats of Minwax Helmsman as a topcoat. This finish
system is on an oak sample and it has some failure areas as was previously reported. There is
separation but no splits on the ends of the boards. The finish is a nice amber color and was very
smooth because the epoxy was allowed to fully cure and it was block sanded before applying the
topcoats. Based on these tests, this finish would probably be acceptable as bed wood finish although
not the most durable.
- Three coats of Pelucid as a seal coat and
three coats of Minwax Helmsman Spar Urethane as a topcoat. This finish system is on an oak sample and
it has some failure area, probably the least of all oak samples. One board has a split on the end and
there are two areas of separation along the edges of two boards. The Pelucid was block sanded before
the topcoat was applied. This finish lasted well before failure and probably would be acceptable as
bed wood finish. Pelucid is not usable as a topcoat, but is a durable seal/primer product.
- Three coats of POR-15 Rust Preventative Paint
as a seal coat and three coats of Behr gloss black enamel. This finish is on an oak sample and it
has no failure at this time. The finish has possibly dulled slightly, but is still very glossy and
sealed well. The finish has lasted much better than the first test series in which we used Behr primer
and topcoated with the same Behr gloss black enamel. Even though POR-15 Rust Preventative Paint is not
specified for wood by the manufacturer, it appears to be an effective primer if it is coated with a quality
topcoat paint. If you plan to paint your bedwood, this finish system should be considered as it is very
durable and easy to apply.
- Four coats of Glisten applied as described in
the earlier update. This system is on an oak sample and failed early in the test. Based on these
tests, Glisten is not recommended for bedwood applications.
- Three coats of Pelucid and three coats of
Minwax Helmsman Spar Urethane on a pine sample. The Pelucid was cured about 4 days and then block
sanded before applying the Helmsman. This finish system is one of the most durable and lasted about a
year before a small separation in the finish appeared. The wood continues to darken slightly, but is
still very attractive. The ends of the boards are still totally sealed and shiny. If you plan to
use pine wood with a natural finish, these tests indicate this is a good choice for the finish.
Periodic refreshing of the topcoat is required for most any finish on wood exposed to the elements and the
Pelucid/Helmsman combination seems to work as well as any. The time before failure occurs depends very
much on the amount of exposure to the elements and will vary with each person's truck and their climate.
- Linseed oil as a primer/sealer and Minwax Helmsman Spar Urethane topcoat. This system is on an oak
sample and it has failed as noted above. Based on these tests, this would not be the best choice for bedwood
applications, although it probably would be acceptable for trucks that are rarely exposed to the weather or
moisture. The finish darkened the wood more than most, likely because of the linseed oil color in
addition to the exposure to the sun.
All the oak samples with natural finishes have some amount of failure. The best in these tests appear
the be sample #6 and sample #1. Oak is especially susceptible to splitting on the ends and special
care should be used to seal the ends as much as possible with the seal coat product. See Sample 6 left.
Both of the pine samples with natural finishes are performing very well and we will continue to observe them
and report the results. See picture left.
POR-15 Rust Preventative Paint appears to be an excellent primer/sealer and when used with a quality exterior
paint should make a good choice for bed wood that is to be painted. See picture left.