Staining/discoloration on white oak lumber
Valleybeach
| Posted in Wood and Materials on
In the recent years we have been having a growing problem with “banding” stain marks on our white oak lumber from our supplier. Typically they are dark lines about 1-1/2″ wide and are spaced a few feet apart perpendicular to the board (see photo). These stains go through the entire board making the boards useless. This most recent batch of lumber has the banding marks but is yellow instead of the darker color (also see in photo). Any ideas on what is the cause? I’m thinking it must have something to do with drying or storage process. Any thoughts would be helpful because this is becoming expensive (and time consuming). Sometimes our suppliers will return the wood and sometimes they wont.
Replies
Surface stains like that could probably be removed by oxalic acid. I'm amazed that banding would cause stains to go all the way through the board. As an experiment, try resawing a piece that has this stain to expose the interior of the stain and try using oxalic acid on that. If it works, leave it for a while to see if it returns.
That would be sticker stain. That will happen sometimes in the kilning process. Typically it would be considered a defect if the amount is extreme. It will happen in any specie if the kiln schedule is not correct.
Thank you bilyo for the quick response. Do you think that this has something to do with the drying process? Transport?? Maybe where it sat on stickers....
I will purchase some oxalic acid and give that a shot. Out of curiosity...why do you suggest resawing it first?
Although oxalic acid is relatively safe, if one is not familiar with using it needs to be aware it is a mucus membrane irritant. You will notice it most when sanding the dry wood after the treatment has dried. If you wipe down the treated area with a damp cloth, you can remove most of the dissolved crystals. If you don't wipe down, be sure to use eye protection and a n95 dust mask.
It’s directly related to the drying process , more precisely to the stickers that are used to space the wood in the kiln. I cannot tell you exactly what the staining process is all about but that is something that should be fixed by the kiln operator , it’s called sticker stain.
Used to see that frequently on poplar. I have been told it is caused by a mold or fungus. It does go below the surface and I know of nothing you can do to get rid of it.
I believe it can be prevented during the drying process.
Maybe find another supplier.
Either the product you received was good or it was defective. While I can't add anything to how to work around the 'sticker stain' Gulfstar mentioned, I would consider escalating the pushback against your supplier. Just cuz the product (lumber) a company delivered is bad, it doesn't mean we consumers (woodworkers) hafta accept it nor be expected to work around it.
Definitely sticker stain. Typically, this is from using green stickers instead of dry, and leaving the stack out in the weather to air dry before kiln drying, where rain can re-wet the area trapped between the board and the sticker. It is indeed caused by mold and fungus, and there are different ones that discolor the wood in different colors. I have usually been able to plane a bit of the surface off and get rid of it, but it does depend on how deep it goes, which can vary a lot.
It sounds from your post that you order your oak in bulk and have it delivered, rather than picking it out yourself. To avoid this in the future, you need to either make an agreement with your current supplier to send you stain free lumber or take back defective lumber, or go get it yourself, or change suppliers (and make clear to the new one what is acceptable and what they will need to take back.)
Sticker stain. You can try oxalic acid, but I don't know if it will work. Beyond that, it's not fixable.
Wet stickers. I had some white pine cut and air dried. The stickers extended out past the pile into the screen that was over the stack. The stickers in the top 2 layers were re-wet with every rain. The stains went deep.
Great feedback from all...thank you. This definitely confirmed my suspicions (except I thought it may have something to do with tannins). I will certainly use this information to push back against our suppliers. Here in the San Fransisco bay area there has been some disruption in the suppliers and it is hard to know which suppliers this is coming from, but I will have my guys be more vigilant in looking for this staining so we can figure out where it is coming from.
Just FYI, we purchase primarily rough 5/4 material, and the staining goes through the entire board about 50% of the time. Often difficult to tell if the board is usable or not until we start milling it down.
It's sticker stain. Sticker stain is oxidative, not biological (not fungal).
Using old logs is a factor, meaning a long time between harvest and kiln drying. Chemical reactions occur during log and green lumber storage, especially in warm weather.
Drying too slowly encourages sticker stain. As someone mentioned, wet stickers also encourage stain. Restacking on dry stickers in slightly different locations after a week can help reduce the issue. Narrow stickers help. Some manufacturers use grooved or slotted stickers the get additional drying under the sticker. The conditions for sticker stain are established when the wood is green, but high temperatures as the wood gets dry can encourage the chemicals to react and darken. This is why lighter-colored hardwoods are often limited to 160F whereas 180F is used for other hardwoods.
An old, but excellent publication on stains is "Causes and cures for stains in dried lumber" by Gene Wengert. I attached it if you're interested. The "cures" part of Gene's excellent advice is directed toward the kiln operator. Unfortunately, there's not much you can do once the staining occurs.
I’ve read that one should only use the same species for stickers as the lumber to prevent this. Sorry if this was stated above. Makes sense.
I’ve stickered red and white oak this way (wood from the same tree) and have never experienced an issue.
You can't go wrong using sticker of the same species as the lumber, but it's not necessary. The root causes of sticker stain are old logs, long storage times, wet stickers, and slow drying.
You are 100% correct, however, if the stickers are from a wood that is a lot darker than the wood being dried. The sticker's history can be a factor in addition to those I mentioned above. I once kiln dried maple using sticker that were previously used on walnut. This stain will not go as deep, but it's still not good.
Just out of curiosity is there a reason we don’t use a plastic e.g. hdpe for stickers?
That is a good question. I hope someone responds. I’ve wondered this myself, makes sense.
I may start a plastic sticker business, but in Canada the feds will shut you down if you even mention the use of plastic - NOT environmentally friendly.
Maybe stone then? 🤔
Bits of concrete?
There’s just got to be something better…
My first thought was trapped moisture with a non-pervious substancè in there. A strip of cloth might solve it though. I think we all pretty much use s-crap for stickers. I would not plunk for hdpe, but I might chop up trex offcuts. Good Q BillieR.
That makes sense! But also I’d imagine having wood ones would stay wetter longer too, and clearly there is some kind of capillary action between the two, given the banding. It’s just interesting really! Maybe there’s a really good reason. Or maybe it’s just done this way because it always has been done this way.