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Ok here's a typical board after re-sanding, doing a hot coat of the above wax/oil mix (pre-heat board for 15-20m at 170F, coat heavily, re-heat for another ~10m, wipe on another coat in the dry spots/smear around the wet spots, then let cool), washed with hot water and dawn dish soap then rinsed and drip dried.
Some observations..
I think I've gone about as far as I'm going to with finishing tests on these. However, I'm not sure I'm done with this topic.. it seems there is some opportunity for a little science based analysis as opposed to the anecdotal bits we've been dealing with so far.
OTOH here's a study from U of W that claims I'm full of it.
http://www.treenshop.com/Treenshop/ArticlesPages/SafetyOfCuttingBoards_Article/CliverArticle.pdf
Specifically they noted that there was no meaningful variation in bacterial counts between mineral oil treated and not. Interestingly they also noted that there was no differentiation in the amount of media uptake (as measured by weight difference before and after exposure to a contaminated nutrient solution). The latter seems to indicate to me that either they didn't do it right, or mineral oil doesn't do squat to prevent moisture uptake (and is thus mostly useless in preserving wood). The "mineral oil" used was "vendor provided" (no other information.. grr), best guess is that it was probably boos block oil. More work obviously needs to be done here as the data seems a bit contradictory.
Also interesting from that study is that moisture uptake is positively correlated with reduced surface bacteria counts (basically the bacteria gets sucked into the wood and is then unavailable for contamination - it appears the wood also de-hydrates or otherwise has antibacterials that kills the boojums, there are a few other interesting studies out there on that - at least one of which contradicts the widely held belief in hard closed pore woods being necessarily better but gave the nod to pine and then oak in order as the most anti-bacterial woods; it was a very specific study on chips though that may not apply to whole blocks. We're getting a bit far afield here though).
Salting the top of boards also has a dehydrating effect on bacteria thus enhancing the woods antibacterial nature (supported by several studies, but I'm getting to long winded already).
Well mineral spirits are pretty volatile so I think they should just thin the mix and yield a thinner film. Turpentine has similar purposes, you do have to be careful of what kind of turpentine to get though as they're not all equal. The value of a thin film is that it oxidizes faster and thus polymerizes more effectively. I'm not really convinced of the utility in this case either but that's the theory.
Some observations..
- Dissection of scrap piece after hot coating showed penetration in excess of 1/8" in places, pretty happy about that. The sub surface appears almost polymerized from the high wax load.
- Some of the boards looked close to dry once they'd finished cooling indicating that I might have been able to get even more wax to uptake with some care.
- At first pass the maple appears to have not taken up the wax as well as the walnut, given that the walnut is a fair bit softer.
- The resulting finish is somewhat mat looking but still has decent depth.
- The finish (after washing) doesn't take fingerprints or anything noticeably.. its also not super glossy but them's the tradeoffs.
- Moisture resistance seems excellent after the first wash, it basically beaded up and dripped off almost entirely within a couple of minutes (by the time I'd washed all 23, the first ones were basically dry).
I think I've gone about as far as I'm going to with finishing tests on these. However, I'm not sure I'm done with this topic.. it seems there is some opportunity for a little science based analysis as opposed to the anecdotal bits we've been dealing with so far.
OTOH here's a study from U of W that claims I'm full of it.
http://www.treenshop.com/Treenshop/ArticlesPages/SafetyOfCuttingBoards_Article/CliverArticle.pdf
Specifically they noted that there was no meaningful variation in bacterial counts between mineral oil treated and not. Interestingly they also noted that there was no differentiation in the amount of media uptake (as measured by weight difference before and after exposure to a contaminated nutrient solution). The latter seems to indicate to me that either they didn't do it right, or mineral oil doesn't do squat to prevent moisture uptake (and is thus mostly useless in preserving wood). The "mineral oil" used was "vendor provided" (no other information.. grr), best guess is that it was probably boos block oil. More work obviously needs to be done here as the data seems a bit contradictory.
Also interesting from that study is that moisture uptake is positively correlated with reduced surface bacteria counts (basically the bacteria gets sucked into the wood and is then unavailable for contamination - it appears the wood also de-hydrates or otherwise has antibacterials that kills the boojums, there are a few other interesting studies out there on that - at least one of which contradicts the widely held belief in hard closed pore woods being necessarily better but gave the nod to pine and then oak in order as the most anti-bacterial woods; it was a very specific study on chips though that may not apply to whole blocks. We're getting a bit far afield here though).
Salting the top of boards also has a dehydrating effect on bacteria thus enhancing the woods antibacterial nature (supported by several studies, but I'm getting to long winded already).
Well mineral spirits are pretty volatile so I think they should just thin the mix and yield a thinner film. Turpentine has similar purposes, you do have to be careful of what kind of turpentine to get though as they're not all equal. The value of a thin film is that it oxidizes faster and thus polymerizes more effectively. I'm not really convinced of the utility in this case either but that's the theory.