wood panels

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Re: wood panels

Postby Sometimewoodworker » Mon May 29, 2017 8:58 pm

canopy wrote:MDF shrinks and expands greatly between the wet and dry seasons of Thailand. And MDF molds quickly even if kept in a dry area. I can't think of how it would be useful for anything yet there it is in the stores.

Sorry neither of your statements are true.
MDF is stable and doesn't change size with humidity changes even if it has no finish on it. Neither does it permit Mould growth if dry.

It does swell and deform if it is in water contact and then you can get mould growth on the damp parts

As it is dimensionally stable it is great for large panels
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Re: wood panels

Postby canopy » Tue May 30, 2017 7:15 am

I tried MDF in the past for making some large jigs. I was shocked how covered in mold it became in the wet season; far worse than any wood I have used. And it also crowned up between screws due to expansion. Perhaps my results are related to the fact I live in the mountains with a lot of rain and dense fog compared to lower elevations. Even real leather left in a bedroom can mold badly here. And towels left on the rack may still be wet the next day during the wet season. For what it is worth, I have found bamboo and rubber wood also mold even if never exposed to sun and rain and are both dimensionaly unstable as well.

Now my experience with teak is different. The sapwood absolutely can mold, but only on newly cut stock. Heartwood and dry sapwood never molds even if left unfinished. The majority of shrinkage occurs in the first months, then dimensional stability becomes excellent.

So with these results in mind I am considering making panels from teak boards and doing glue ups. It's a lot of work and it would be preferable to find sheets of something sold that can simply be cut to size. I just haven't heard any good alternatives yet.
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Re: wood panels

Postby Klondyke » Tue May 30, 2017 10:00 am

canopy wrote:I tried MDF in the past for making some large jigs. I was shocked how covered in mold it became in the wet season; far worse than any wood I have used. And it also crowned up between screws due to expansion. Perhaps my results are related to the fact I live in the mountains with a lot of rain and dense fog compared to lower elevations. Even real leather left in a bedroom can mold badly here. And towels left on the rack may still be wet the next day during the wet season. For what it is worth, I have found bamboo and rubber wood also mold even if never exposed to sun and rain and are both dimensionaly unstable as well.

Now my experience with teak is different. The sapwood absolutely can mold, but only on newly cut stock. Heartwood and dry sapwood never molds even if left unfinished. The majority of shrinkage occurs in the first months, then dimensional stability becomes excellent.

So with these results in mind I am considering making panels from teak boards and doing glue ups. It's a lot of work and it would be preferable to find sheets of something sold that can simply be cut to size. I just haven't heard any good alternatives yet.


I have hundreds of jigs made both of MDF and solid wood (mostly acacia, oak), laying, hanging over the years where the humidity is also quite high, however not overly. I haven't noticed any larger problems with a mold, fungus. Perhaps since it is in a large space of factory, no lack of an air draft through, occasionally enhanced by placing a strong blower from machines around.

If your humidity is really so high, hence building the mold, you can apply a lacquer. A transparent NC (NitroCellulose) lacquer - or just the primer sealer - is fast drying, closing properly all the pores, at MDF quite excessive.

But also every wood invites in the moisture by its open pores. The teak contains an oily lignin (more than other species), thus sealing the pores after some time. Therefore so suitable for keeping over ages. However, the teak too expands and shrinks similarly as any other species. Can be observed at entrance doors and cabinets even after many years in the old village houses. Depends on the season, either they can be easily closed or they stick in the frame, sometimes cannot be fully shut.

Important to seal mainly the cuts where the pores of the grain are mostly open. The lacquer will really make the trick, creating (almost) unpenetratable surface. Attaching pictures of (salad) acacia bowls (our production) serving dog food, mostly a rice in a liquid state, sometimes laying there over half day till the next food supply. And sometimes laying in the garden (and full of water) where the dogs (labradors) like to bring it - from not very clear reasons. That's why we had replaced the usual ceramic bowls since often broken. Also an acacia bowl mounted on a lazy hammock, in an open air, sometimes fully of rain water during the day, sometimes exposed to a full sunshine.

Image


Image
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Re: wood panels

Postby canopy » Sat Jun 10, 2017 8:00 pm

Just to drive home the point about MDF. I recently had something delivered. It was enclosed in an MDF box for shipping. After sitting for a while in this climate, it became covered in green mold. The box stayed indoors, was well aerated, and never had any water contact. Some materials that work well in other countries are not such a good idea in Thailand.

mdf.jpg
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Re: wood panels

Postby Sometimewoodworker » Sat Jun 10, 2017 10:37 pm

canopy wrote:Just to drive home the point about MDF. I recently had something delivered. It was enclosed in an MDF box for shipping. After sitting for a while in this climate, it became covered in green mold. The box stayed indoors, was well aerated, and never had any water contact. Some materials that work well in other countries are not such a good idea in Thailand.

The attachment mdf.jpg is no longer available

It must be your location.

P2272628.JPG


The dividers in my work bench made about 10 years ago have had nothing done to them, no, finish, and apart from being a bit dusty are as good now as they were then
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