Locus sign for farm

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Forum topic by Mystang89 posted 11-06-2017 02:21 PM 741 views 0 times favorited 6 replies Add to Favorites Watch
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4 posts in 1010 days

11-06-2017 02:21 PM

I purchased a farm which had lots of locus trees which needed to be felled. Out of love of those locus trees I decided to make a sign for our farm which was going to be seen from the road. I want to keep the original grain and everything. No paint, no stain but I need something to protect the wood from the elements. One thing that is already starting to happen is mold and that is only after 5 weeks or so of it being out.

I looked up boiled and raw linseed oil and found they were good for protection from elements but attracted mold. Already have that problem.

Did a bit of searching and found people saying acrylic waterborne would be good too. Also saw enamel spray but couldn’t see if it would protect the wood from mold or if there were any negatives to using it.

A friend recommended sparathane. Thoughts?

I’ve used polyurethane before. Not good for outside use.

Someone else recommended copper coat but it seems that “Freshly applied COPPERCOAT dries to a rich copper brown. After immersion COPPERCOAT oxidizes to a dark, verdigris green color.”

Looked at creocoat as well but it seems that creocoat inparts a dark color when it dries as well. Can anyone verify this?

What would be the best solution which wouldn’t attract mold, last a reasonably long time, doesn’t yellow from UV over time and helps to keep the wood from turning ash color?

6 replies so far

View sras's profile


5536 posts in 3937 days

#1 posted 11-06-2017 03:48 PM

For outdoors, I use marine grade finishes.

-- Steve - Impatience is Expensive

View runswithscissors's profile


3107 posts in 2833 days

#2 posted 11-11-2017 02:04 AM

I suspect that if the wood was green, the moisture in the wood attracted the mold. Locust has a reputation as an extremely durable wood (though I don’t know about the sapwood in that regard).

Rather than trying to save the moldy sign, I’d dry the locust over several months before making your sign. The dry wood should give you much better results (even though it will get rained on, the mold problem shouldn’t be so severe.)

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

View sawdustdad's profile


379 posts in 1693 days

#3 posted 11-11-2017 03:43 AM

Locust? Black Locust? They make fence posts out of locust. I just sold our old homestead. It has locust fence posts that I installed in 1981. Literally, 36 years ago. They are still solid as a rock. (At least the 5×5 gate posts are.) Many of the line posts only lasted 25 years. In direct ground contact, with no treatment.

So do you need a finish on a locust sign. I don’t think so.

-- Murphy's Carpentry Corollary #3: Half of all boards cut to a specific length will be too short.

View Mystang89's profile


4 posts in 1010 days

#4 posted 11-11-2017 12:36 PM

The wood was cut down in late winter last year 2017 and has been covered from rain for about 3 months. I don’t know how long it takes to season because the sign is coming from a 6’ log shop maybe it takes much more time for it to season than a normal 2’ log? Either way it definitely has mold on it.

Yeah, it is black locus by the way. I had to rebuild a fence line and had a ton of it. I had just cut this one too short in my rush.

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4 posts in 1010 days

#5 posted 12-03-2017 03:00 PM

So I decided to just spar urethane water based. It says it’s superior uv protection, mold & mildew resistant and seals out water. It specifically states that it is for exterior use.

Today I went outside and there was coat on my sign so I wiped it off. It took some of the urethane with it! This is after 3 coats.

Sometimes PLEASE tell me what’s going on?!

View HerbC's profile


1805 posts in 3667 days

#6 posted 12-03-2017 03:48 PM

1. The slab of lumber is still “wet”, it will probably take a year or more to dry enough to be “finished” with any kind of coating or preservative. The polyurethane will not properly adhere to the surface of the wood due to the excess of moisture in the wood.

2. There is NO good solution that provides a transparent/clear coat for external use items. The closest thing that I’ve read of (haven’t tried myself…) is untinted exterior paint base (oil based)...

-- Herb, Florida - Here's why I close most messages with "Be Careful!"

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