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MDF troubles
Tuesday, April 6 2010
When working with various materials, I have many years of experience, some of which has been supplemented by the experiences of my ancestors and handed down father-to-son from countless generations into Bavaria and beyond. (You'll have to indulge my sexism here, as my mother contributed relatively little to my knowledge of materials.) But the problem with father-to-son information is that it depends entirely on the interests of the fathers. They learned what interested their fathers, and supplemented this with other information they learned on their own. And I've had to do the same. My father provided a lot of first-hand knowledge of wood species, wood grain behaviors, nail and screw techniques, basic dimensional carpentry, fencing, roofing, hole excavation, galvanic corrosion issues, organic gardening, handsaw-powered tree felling, and concrete mixing. But I've had to teach myself stone masonry, drywall, automotive repair, electricity, electronics, plumbing, power tools, treated lumber, and welding. Occasionally I still find myself working with new materials I don't understand well enough to avoid major mistakes. One such material is MDF (medium-density fibreboard).
Because of its flawless smoothness, it seemed like an ideal material for the brownhouse's "shitting bench" — the place where the toilet seat and sink sit. I wanted a material I could coat with multiple layers of polyurethane and occasionally sponge down (as one does on surfaces in a bathroom). The problem with MDF started materializing at some point this winter when I noticed the surface of the bench had begun to swell and bulge around the penetration where the vent stack rises up through the brownhouse cabin on its way to carrying noxious gases from the shit chamber to somewhere above the roofline. Gradually this zone of swelling expanded outward like a slow-growing tumor, metastasizing into formerly-good MDF. I assumed that the problem was moisture condensing on the outside of the vent pipe and then running down into the MDF. (I never actually observed this phenomenon and certainly hadn't anticipated it.) By March, the swelling had reached the place in the MDF where the toilet seat cover was attached, lifting it up and providing a gap for fragrant gases to enter the cabin. Soon thereafter I had to lengthen the metal rod that depresses the normally-on vent fan switch when the seat is down; otherwise the fan would have been on all the time. I tried caulking around the gap where the vent stack punched through the MDF, but evidently the damage had already been done and there was no arresting the cancer.
So today I used chisels and a power saw to cut out a roughly-square section of MDF around the vent stack and up to the edge of the shit hole. As expected, the swollen MDF was soaked with water, though once it was gone, the underlying OSB (which hadn't swelled noticeably) dried out quickly and could be polyurethaned in anticipation of whatever I end up using to resurface that part of the shitting bench.
In the late afternoon I drove into town to get some supplies for this project as well as other needs. One of these was pseudoephedrine for recreational use, so I had to ask for it at ShopRite's pharmacy counter, where the young man checked my driver's license and entered me into a database on the chance that I might be supplying raw materials to a manufacturer of methamphetamines. As I took my drugs, the young man said something positive about the teeshirt I was wearing. It's a 2600: Hacker Quarterly tee shirt, and not many people are hackers and fewer still know about 2600, so he was making sure I knew that he was part of the tribe. I gave him a thumbs-up, which is probably an inappropriate shibboleth. But I didn't think to do something nerdier like a Vulcan handgina.
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