Paraffinic / Linseed oil

[RPetry 564]

More fun. A stain manufacturer and I have been having discussions on the susceptibility of boiled linseed and paraffinic oils to mildew, mold, and general discoloring due to moisture and environmental exposure.

I have agreed to a test. It has been approved by the other party. Any suggestions would be welcomed.

Western Red Cedar 2 x 6 board, new wood purchased last year and never stained or exposed to the weather. It has been cleaned with Restore sodium percarbonate wood cleaner, lightly pressure washed, and brightened with citric acid a week ago. The citric was gently washed off with water after about an hour of brightening.

The cedar is very dry, Delmhorst reads at 8%. It is in my office at the moment.

The plan is this. The cedar board will be divided into 4 sections. One section will be treated with boiled linseed oil, the most common oil in exterior wood stains. It has been confirmed by the manufacturer that it does not contain any fungicides/mildewcides.

One section will be treated by paraffin oil. No Ken, not baby oil, one refining step down. Again as with the linseed, no additives.

One section will be untreated and left alone. The last section will be wrapped in plastic.

Both the linseed and paraffin oil will be allowed to dry inside for at minimum a week. Reason for this is it is Spring, and I do not want any pollen to accumulate on a "tacky" surface.

The board will then be set outside my home in a shaded area, about 1.5" from the ground to encourage moisture exposure.

Any suggestions on protocol are welcomed.

[Beth n Rod 1,278]

Sounds like a very fun test! Can't wait to see what happens!

Beth

[RPetry 564]

Beth,

Don't hold your breath. Results will take a while....

[Beth n Rod 1,278]

I know. But it will still be fun! :)

Beth

[plainpainter 217]

painters watch paint dry and deck guys watch mildew grow....interesting!

[RPetry 564]

Ok, ready to put the test board outside.

First pic - 2 x 6 western red cedar, about a year old, never been outside. Prepped with sodium percarb and citric acid as described in the above post.

Second pic - Paraffin oil on the left, boiled linseed oil on the right. Put ~ the same amount of oil on both sections.

Third pic - Full board after a week of inside drying. Note that the paraffin oil has migrated laterally into about half of the untreated cedar section. About 1/3rd of the linseed section is "shiny", but neither oil is tacky and both are fully dried.

It now goes outside and we'll see in 6 months to a year if there is any mold/mildew growth.

[plainpainter 217]

you're really bored, Rick! LOL!

[PressurePros 248]

Tanning oil! :D

[RPetry 564]

you're really bored, Rick! LOL!

Daniel,

Your presumption is false. Life is too interesting to be bored...

Tanning oil! :D

Ken,

Yeah, like we need it. Last saw the sun on Sat. between rain showers. Doesn't look like we'll see it for another 5 or 6 days. A real tough spring...

[Beth n Rod 1,278]

I like Rick's experiments!

Beth :sunshine:

[hoosierwindowtek 14]

Rick,

I know you've already done a lot of work on this sample board, but for future reference it helps to cut a little groove in the board between areas you're staining to keep the oil from migrating from one area to another. You can do this with just a utility knife or for more resistance a saw would work better. I made a display board to show customers different stain colors that way and I have several different stains side by side on one board and they stayed separate.

H

[RPetry 564]

Richard,

The test board was not much work, but your point is well taken. I only have 5 or 6 sample boards from stain manufacturers that do exactly that!

I can almost guarantee that the paraffin oil would have migrated through the wood laterally regardless of any groove.

[PressurePros 248]

In the end, each stain will have its good and its bad and all boards will need to be redone in two years. I'm not knocking the experiment Rick. I enjoy reading your unbiased reviews. You know me, I don't get into this the same way you do. Its a business for me. I take pride in my work but knowing the details as to when mold grows, which is more conducive to maintenance, etc doesn't interest me unless it takes me past the two year mark on longevity.

[RPetry 564]

In the end, each stain will have its good and its bad and all boards will need to be redone in two years. I'm not knocking the experiment Rick. I enjoy reading your unbiased reviews. You know me, I don't get into this the same way you do. Its a business for me. I take pride in my work but knowing the details as to when mold grows, which is more conducive to maintenance, etc doesn't interest me unless it takes me past the two year mark on longevity.

Ken,

Fair enough. This is a interesting test with a stain manufacturer and yours truly.

Odd thing, the Forest Products Lab has never, in my search, done anything on paraffin oils, but they have certainly warned of potential mold/mildew with linseed oil.

Regardless, if the stain manufacturer has used correct and high quality driers and mold/mildew/fungicides, the oil base should not matter, at least for the short term.

Two years on horizontal wood exposed to direct sun, for semitransparent oils in our climate, is the norm.

I'm almost willing to make book. Wanna' bet?

[Beth n Rod 1,278]

It was a wet spring...please report so far!

Beth

[RPetry 564]

It was a wet spring...please report so far!

Beth

Its a big 10 - 4 on that, good buddy! Real wet spring, maybe the weather patterns will change with the summer solstice!

Pic attached taken a half hour ago. The "dark" section is boiled linseed oil, the section immediately to the left is parafin oil.

There might be the start of something, note the few black areas in the linseed section. Also, the top half of the parafin section shows some slight discoloring.

Remind me to check it in another few months.

[Beth n Rod 1,278]

Will do! ;)

Beth

[MudDuck 20]

Is that what you call a "Petry" dish? Rick ya got some nice green stuff on the building next to the board I see. Could I intrest you in a house wash?

[RPetry 564]

Is that what you call a "Petry" dish? Rick ya got some nice green stuff on the building next to the board I see. Could I intrest you in a house wash?

That is a POS privacy fence between townhouse units. That is why I chose the location of the test board, very little to no direct sun and wet.

[Beth n Rod 1,278]

BUMP!

It's been so wet, post another update!

Beth

[Tmrrptr 164]

Good exhibit to show clients !

[RPetry 564]

It has now been ~ 4 months since this little experiment started. Pics as follows:

Pic #1 - Four sections of the test cedar board. From left to right, untreated cedar, paraffin oil, boiled linseed oil, untreated cedar wrapped in plastic.

Pic #2 - Closer shot of the untreated, paraffin, and linseed oil sections. Discoloration was evident on all three, with the linseed oil test section darker and most noticeable.

To determine whether this darkening was dirt and/or mold/mildew, a 3% sodium hypochloride drop was applied to the three sections. Immediately below the "drops", a water/Dawn soap solution was applied and scrubbed with a toothbrush.

Cleaning with the soap/water solution shows no visible difference. There is no doubt that this is mold/mildew.

Pic #3 - A close up of the paraffin oil (left), and the linseed oil (right) sections.

Initial conclusion: The untreated and paraffin oil cedar sections are virtually identical in appearance and mold/mildew growth. From a layman's perspective, it could be deduced that pure paraffin oil does not promote growth.

The boiled linseed oil section is harder to interpret. The earlywood is clearly much darker in appearance than the latewood, which is to be expected as it is more "porous" and absorbs more oil.

Visually, it could be concluded that there is more mold/mildew growth due to boiled linseed oil than either paraffin oil or untreated cedar. But other factors, for example discoloration due to UV or wood/oil chemistry changes due to environmental exposure could be the cause. It would take sophisticated laboratory analysis to find an answer.

I'll put the test board back outside, and take another look next spring.

[plainpainter 217]

In retrospect I think having 4 of these boards with one treatment each would have been better. I don't know about the bleach drop test - as that could take out color even without any mildew? All in all the whole board looks pretty clean to me

[Beth n Rod 1,278]

Very interesting.....

Beth

[Ethan 14]

Ken,

Fair enough. This is a interesting test with a stain manufacturer and yours truly.

Odd thing, the Forest Products Lab has never, in my search, done anything on paraffin oils, but they have certainly warned of potential mold/mildew with linseed oil.

Regardless, if the stain manufacturer has used correct and high quality driers and mold/mildew/fungicides, the oil base should not matter, at least for the short term.

Two years on horizontal wood exposed to direct sun, for semitransparent oils in our climate, is the norm.

I'm almost willing to make book. Wanna' bet?

I completely agree. It's the quality of the resins, mildew/fingicides and driers.

[Beth n Rod 1,278]

Is it time for another photo? How is this going?

Beth