White Pine problems with sapwood

[Greenie]

We make routed signs for state parks out of white pine. We cut our own, air dry for the summer and then we put it inside, still on stickers. We prefer clear wood so we have been using sapwood. Lately some of the signs have been splitting once they're installed in the sun and weather. Some signs form deposits on white sap residue on the surface - these same sections tend to absorb water like a sponge which makes them rot faster.
Wood we work on has been air dried and stored inside for at least a year, moisture tends to be about 13-16%. Once in the heated shop it checks quickly.
Anyone have any suggestions of what we can do differently?

Thanks!

[beenthere]

Greenie
I'd think you could add some water repellant preservative to the signs after completed, and before submitting them to the elements.

If that dry, then the preservative should soak in (I'd dip them for a period of time to get better penetration).

I'm surprised the state doesn't require the signs be preservative treated in their contract. A bit of a waste of tax money to not require it, seems to me.  : :

Lower the temp. in the heated shop to get higher humidity, and avoid the quick checking that you experience.
What humidity is the air dried lumber stored at for at least a year?  Or is it not air dried when going into storage?

What state or area are you at?

[Greenie]

I'm in Maine, along the coast. Ambient humidity for our lumber stored in an unheated building ranges from 13-16%. There's no contract, we do the signs in house.
I like the idea of sealing or treating the signs before they go in service - would that keep the sap from weakening the lumber?

[SwampDonkey]

I was wondering too why you have checking so bad in your pine. I have pine, even stained and knotty pine that hasn't a check in it. I just squared and planed some up today for a top on a chest I'm making. It's all been air dried in the barn for 7 or 8 years. The one mistake though, is it should have been kilned to kill the dang ambrosia. When that came off the mill it wasn't stained, the fungus grew in the barn as it was warm and humid and the air flow wasn't great other than it was stickered good. It gets quite warm up where it was stored. It is all open up there though and no floor. I have a door I could open but that lets birds in.

[beenthere]

I'm in Maine, along the coast. Ambient humidity for our lumber stored in an unheated building ranges from 13-16%. There's no contract, we do the signs in house.
I like the idea of sealing or treating the signs before they go in service - would that keep the sap from weakening the lumber?

Don't understand that question about sap weakening the lumber...any pics of what is happening and when during the time the blanks are in storage and showing 'signs' of failure?

[Greenie]

Where the sap residue appears the wood is more absorbent - areas that don't have sap residue on the surface dry quickly after a rain whereas the parts of the sign (joined) that have sap residue on the surface allows water to penetrate like a sponge. A few years out in the weather and the absorbent sections rot.
I'm not sure if the sap breaking through the stain and accumulating on the surface in the form of white powder plays a role in the breakdown of the pine or if it becomes absorbent due to the makeup of the sapwood.
BTW... I spray a strong solution of bleach and water on the surface of the pine boards (and planks) prior to stickering them - doing so has all but eliminated sapstain.

[SwampDonkey]

Well areas of sapwood had active live wood, sapwood, which continues to ooze sap even in log form. You'll see the outside rings ooze sap. And of course that is where the fungus and bugs like to make home. It is likely that a fungus is getting a hold of the wood to make it break down, not the rain. And of course that sap coming through on your signs is because the sap wasn't "set" by kilning. It will continue to bleed for a long time and out in the weather, while fungus have a nice treat. Might be a powdery mildew making that white powder on the signs, growing on the sap. Bleach doesn't eliminate fungus, need borox I think. There are other fungus that can get into stacked pine that are about the same color as the wood and you can sometimes see a paper like film on the surface or another might be a moldy fuzz. Mold I think is just superficial and doesn't cause break down of the wood in most cases. Might be a confusion of what your bleaching. On the other blue stain thread you can see blue stain and no bleaching will remove that, it goes into the wood. I'm not an expert in this field but that's my assessment for what it's worth.

[Greenie]

The bleach & water mix is sprayed on both sides of pine boards when they are sawed. I am fairly certain that it cuts down sapstain because one year we just treated one side of the board and sapstain sometimes appeared on the untreated side but not the treated side.
Interesting about a kiln "setting" the sap - that makes sense.

[SwampDonkey]

I suspect bleach is only effective if fungus is present to be begin with. I'm not so sure it would be any better than using a solution of floor cleaner in the water such as Lysol, only the bleach is cheaper and non staining.  As soon as the bleach is dried up it's benign, salt and evaporated water. The salt I would think is pretty minute in concentration.

If that lumber stays green (not the color green), long enough and you get ambrosia, which basically farm the fungus, that fungus will travel from cell to cell of the wood. Your probably safe from them if your lumber gets down in the teens in moisture content fairly quickly. Bleach isn't going to penetrate the wood to take the stain out, nor is anything else. It will remove superficial mold and spores already present and that is about it. Borox I think kills any returning spores from the air before it takes a hold. If you can treat the wood with something to either keep the moisture down or keep fungus from taking 'root' you will be ahead of the game. I'm not sure whether borox is the end all solution when your putting signs out in the elements. I think pressure treatment with a preservative is the only solution long term.

I have a shower stall I never use and it is dry and yet fungus returns as I only use bleach on it. So basically, it's not much of a preventative.

[copper green]

Ed Get Copper Green Wood Preservative from Lowes or Home Depot. Soak wood in it and forget about it for 20 years or so.
Guy