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As part of our business we supply large section wooden mantels for above wood burning stoves and have recently acquired a large amount of spalted sycamore. We supplied one to a over a year ago and the customer complained recently that it is has changed colour. How can I prevent this happening in future? We normally finish our mantels with 4 coats of danish oil. Can it be treated in some way to prevent the spalting process. Potential customers love the look of the black lines through the wood but I don't want any more complaints!
The color change may be from oxidation
"Can it be treated in some way to prevent the spalting process."
Thank you so much for your input. I should explain a little further. The spalted timber mantel I supplied over a year ago had started to increase one of it's darker areas. It appears to have continued to 'spalt/decay' in spite of it's obviously dry/warm location. I have been investigating this further myself and suggestions made to prevent this situation occuring in future include:
You can use a two part bleach, which will make all the wood whiter, but not the black line.
Then, I would use a really clear acrylic spray applying the first few coats really dry mist coats, sprayed from further out than normal, rather than really wetting it out. After it is sealed, you can go ahead and build a normal film coat if you feel like it needs it.
Thanks for this advice Keith. As I have quite a lot of this type of timber and I will a few options on some small samples and decide which turns out best.
Are you properly drying your lumber? Or are you finishing and installing wet wood?
Hi Jerry, I see where you are going with this and you are probably correct! The timber we use for large section mantels tends to be quite freshly milled. We have started milling our mantel stock well in advance and leaving it to air-dry for up to a year. Because we make mantels in sections from 6"x4" up to 8"x8" we do no consider kiln drying. In our experience, all that happens is they tend to twist and crack quicker - due to the differential shrinkage between the centre and outside of such large sections! I agree that wet spalted timber will continue to spalt but had hoped it could be prevented in some way, other than having to wait an age for it to dry completely? I have heard of laminating layers of kiln dried wood but this is just cost prohibitive! At what moisture content would you suggest the spalting would stop? All ideas welcomed.
Sorry to have to burst your bubble but If you continue to install wood at those dimensions you will have nothing but problems. There is no magic bullet to cure your problem. You need to drop the moisture content through the entire thickness to the point that the fungus becomes in active. One year is not enough. I would expect future problems for any thing you have installed since the wood will continue to lose moisture and change dimensions, split crack and other chaos. As to the finish oil will always cause the wood to darken, tung oil less so. You need to use a water white clear coat, water base would cause the least color shift I belive. Well good luck with your endevore. I hope I was at least helpful.
If you are putting wood in a house that is that wet, and partially rotten, color is only one of your problems. I'm shocked you haven't been called back for having bugs crawling out of it. You are really opening yourself up for trouble, including having to pay to have a whole house fumigated. If you need big timber dried quickly with no degrade, find someone with a vacuum kiln.
What is the ,moisture content of this wood?
using spalted wood without drying is asking for big trouble. The live virus in the wood is not healthy. I kiln dry all my spalted lumber to kill the virus. I would suggest you do the same as well as for stopping the bugs and shrinkage issues.
Thank you all for your contributions to this topic. We have decided to withdraw all spalted woods from mantel options meanwhile. I will let our spalted timbers air dry for a year or two and then kiln dry. We will restrict the thickness to no just over two inches thick and will not use this type of wood for mantels in future for all the reasons highlighted!
You are right Rich. A fungus. My mistake.
James, from all my reading and studies spalting doesn't stop until under 20% MC. 2nd... just because you pull the spalted off the market till later, ANYTHING green and sealed with moisture are subject to fungus and mold....there are some finishes that "breathe" but I don't know if they breathe enough to release the moisture BUT then logs in log homes have a high MC and are usually way over 20% and I'm not seeing the mold or fungus growing under the finish unless there's another water issue. I'm not a finish knowledged person to address the correct finish. Many yrs ago some exterior repellents WERE causing a mold/fungus growth but I think they found it to be parafin related.
Did thomebody thay thpaled Thycamore?