Replies

1. 
   jonsherryl | Jun 22, 2004 03:12pm | #1

   Jim, keruing is an attractive wood with reasonably good working characteristics. The downsides are it sometimes contains silica that will dull blades quickly and it can also be quite resinous. The resin gives it good decay resistance for exterior projects, but it tends to clog sander belts and may prevent some finishes from thoroughly curing...or it may bubble up under them. Be sure to test your choice of finish on scraps before applying it to the main project. 

1. 
   Jim_McGee | Jun 22, 2004 06:52pm | #2

   Jon,

   This wood has been racked indoors for some time. Is wiping the surface with lacquer thinner prior to finishing enough when resin deposits are present, or will the resin continue to push to the surface over time, making it best to discard those boards for other projects?

   Thanks,

   Jim

1. 
   jonsherryl | Jun 23, 2004 03:55am | #4

   Jim, wiping down the surface might help make it temporarily more receptive to glue, but resin tends to bleed out of a wood as a function of changes in humidity. Typically it beads up on the surface when the wood's moisture content drops and the wood shrinks.

   I'm not suggesting that the wood is unuseable, but only that high resin content is one of its characteristics that must be taken into consideration. You'll probably notice that your inventory contains some boards that are heavier (usually darker in color)and waxier to the touch than others. As you sort the stock for this project cull them out for structural parts below the deck and use the less resinous material for the decking itself.

2. 
   nikkiwood | Jun 23, 2004 03:31am | #3

   Jon,

   Maybe you can answer this question: years ago, someone gave me a tip about a wood that I almost surely remember as Apitong. It was supposed to be great for outdoor uses, and I did look up a local supplier, who in turn warned me off this wood. He said his stock was sold almost exclusively to people making skid beds for semi-truck trailers, because it was hard and tough.

   Because of the high silica content, he said it was murder to mill and fabricate, so I just gave up on the stuff without trying it.

   Is Apitong really that bad?

   Since this fellow has a free stash to work with, maybe dull blades and bits is a reasonable price to pay for making something useful from the wood.

   Any further comments?

1. 
   jonsherryl | Jun 23, 2004 04:10am | #5

   Silica content is a function of the soil the tree grew in. Not all apitong is bad, but when it has a high silica content it is very hard on blades. You can usually spot stock with high resin content, but there are no reliable clues for spotting high silica content until your blades start to smoke.

   I don't mean to give apitong a bad name. It's a very strong, decay resistant timber and it has a lot of appropriate uses. Its warm, reddish brown color and vaguely mahogany-like appearance make it attractive. But you do have to be very careful in stock selection. This is definitely not a wood you would want to try out your new set of carving tools on.

1. 
   Jim_McGee | Jun 26, 2004 06:01pm | #6

   First let me thank Jon for his feedback. The fact that Keruing is made up of multiple species is evident when sorting boards or even looking at the stacked lumber. As Jon said it's obvious which pieces have a high resin content and I'll put those aside for use outdoors. The bulk will be used for a family room floor.

   Nikkiwood hit the nail on the head (no pun intended) about the free wood making it worth sacrificing a few bits and blades. I've bought a "sacrificial" T&G set and a good quality Freud ripping blade. I'm planning on resharpening both after the project.

   One final question for Jon. I'm planning on using Varathane semi-gloss hardwood floor finish. Other than normal sand and prep, assuming I'm using pieces with no obvious resin present, is there any special prep required for Keruing?

   Thanks again,

   Jim McGee

1. 
   jonsherryl | Jun 26, 2004 06:53pm | #7

   Jim, I think the greatest risk you face with keruing, vs most other woods, is that the resins in the wood will have a tendency to bubble up. This should be less of a problem in an interior environment than it would be for exterior decking...but it's still something to think about...especially if you live in a climate that experiences wide swings in humidity.

   I'm not an expert on the chemistry of various finishes, but you might want to consider applying a sealer coat of shellac prior to putting on the harder top coat. Also, I'd avoid using a polyurethane of the type that cures (polymerizes) in a way that makes it impervious to even its own mineral spirit vehicle. These finishes are virtually impossible to repair without heavy sanding...and they're so hard they tend to chip. I think the brand you mention is a good one and specially formulated for this purpose, but I've never used it. When it comes to hardwood floors, I'm a traditionalist. I prefer shellac. It isn't particularly durable, but it's easy to repair...and there's something about the slight amber pigmentation it adds that is particularly attractive to me.

   Hopefully you'll get some other opinions on this from some of our Knots finishing pros. It's a very subjective topic.

2. 
   Jim_McGee | Jun 26, 2004 07:17pm | #8

   Jon,

   Asking about finishes is kind of like asking whether blondes or redheads are more attractive. You'll get some emotional responses!

   Using shellac as a seal coat is a good idea and so obvious I'm kicking myself for not thinking of it. I'll try the amber and blond to see what color looks best on the wood. BTW, I'm in the Philadelphia area so we get significant swings in humidity with the seasons.

   As for using it as a top coat, I've always thought it didn't wear very well and one end of the room will be a high traffic area. What's your experience?

   One other thought I had was that since the wood is so damned hard and tough I might just finish it with oil. It would be easily repaired and/or touched up and it would give this informal room an informal feel. A carpet runner would provide protection for the high traffic area.

   Thoughts? 

3. 
   jonsherryl | Jun 26, 2004 07:36pm | #9

   Penetrating oil would be another option. Keruing is dense enough that it has good wear properties and wouldn't need much protection. Personally, I don't like the dull look of oil on a floor. I like shiny floors, but that's purely a matter of taste. If you go with shellac, you can plan on some periodic maintenance in high traffic areas, but it's easy to do.

4. 
   nikkiwood | Jun 26, 2004 08:41pm | #10

   You are certainly correct that floor finishes provoke almost emotional responses -- every one seems to have their favorite (and hence consider any alternatives to be inferior).

   If you decide on anything but shellac, I would support Jon's wise suggestion to first lay down a sealer coat of dewaxed shellac (I assume you know about Zinsser's Seal Coat, which they have dewaxed for you). Even with the resin content, this should allow any kind of oil or polyurethane finish to adhere just fine.

   Somebody here mentioned the oil based Varathane products, which has been the floor finish of choice for me over the years. It has held up extraordinaily well, even in high traffic areas.

   You can keep a polyurethane floor finish looking good indefinitely -- if you are willing to give the floor a light screening and another coat of poly before you see obvious signs of wear. If you wait until the original finish starts to show wear, then you do have to resand to get the old finish off.

   I hope you will let us know how this wood works out for you.

5. 
   datachanel | Jun 26, 2004 09:13pm | #11

   I haven't actually worked with this wood, but I would like to point out the importance of using a dust mask or dust collection system when sawing lumber with silica.  Potters and ceramacists can attest to the dangerous effects of silica on the lungs.  Good luck with the deck.Datachanel

   Doing things the hard way

6. 
   Jim_McGee | Jun 27, 2004 04:34pm | #12

   > Potters and ceramacists can attest to the dangerous effects of silica on the lungs. 

   They might but I don't. Please explain.

   BTW, I had figured on using a good mask and my shop has dust collection.

7. 
   datachanel | Jun 27, 2004 06:58pm | #13

   I'll be happy to do my best.  One of the key ingredients in clay is silica (glass).  So when mixing clay from scratch it's easy to get dust in the air, and even as clay dries and is worked silica dust will get in the air.  As a result in a ceramics studio you never sweep, you usually sponge or mop dust up, or spend several thousand on a vacuum with an appropriate filter.  As to the effects of silicosis I found some information at the National Library of Medicine at http://www.nlm.nih.gov/medlineplus/ency/article/000134.htm

   and I'll include a section here in the post.

   Silicosis is a respiratory disease caused by inhalation of silica dust which leads to inflammation and then scarring of the lung tissue.

   Three types of silicosis are seen:

   simple chronic silicosis -- which results from long-term exposure (more than 20 years) to low amounts of silica dust. Nodules of chronic inflammation and scarring provoked by the silica dust form in the lungs and chest lymph nodes. This disease may feature breathlessness and may resemble chronic obstructive pulmonary disease (COPD).

   accelerated silicosis -- occurs after exposure to larger amounts of silica over a shorter period of time (5-15 years). Inflammation, scarring, and symptoms progress faster in accelerated silicosis than in simple silicosis.

   acute silicosis -- results from short-term exposure to very large amounts of silica. The lungs become very inflamed and may fill with fluid, causing severe shortness of breath and low blood oxygen levels.

   Progressive massive fibrosis may occur in simple or accelerated silicosis, but is more common in the accelerated form. Progressive massive fibrosis results from severe scarring and leads to obliteration of normal lung structures.

   Causes, incidence, and risk factors   

   Silica is a common, naturally occurring crystal. It is found in most rock beds and it forms dusts during mining, quarrying, tunneling, and work with many metal ores. Silica is a principal component of sand, so glass workers and sand-blasters also receive heavy exposure to silica.

   Risk factors include any work that includes exposure to silica dust. Mining, stone cutting, quarrying, road and building construction, work with abrasives manufacturing, sand blasting and many other occupations and hobbies involve exposure to silica.

   Intense exposure to silica may result in disease in a year or less, but it usually takes at least 10 or 15 years of exposure before symptoms develop. Silicosis has become less common since the Occupational Safety and Health Administration (OSHA) instituted regulations requiring the use of protective equipment which limit the amount of silica dust inhaled.

   I will point out that you're not working with silica in it's powdered form, and that potters are working with it everyday for years.  But it's good to be aware of potential risks.

   Datachanel

   Doing things the hard way

   Edited 6/27/2004 12:01 pm ET by datachanel

8. 
   Jim_McGee | Jun 27, 2004 07:22pm | #14

   Sounds like the risks aren't that much worse than wood dust. I'll be working with dust collection and a dust mask so I should be OK.

   I agree it's good to be aware of the risks though...