Several months ago I was the recipient of a couple of old whetstones in shopmade wooden cases. They had been heavily used for a time and then put aside for many years, which left them covered in hard and smooth layers of dried oil. I attempted to sharpen a chisel with them, but all I ended up doing was dulling it on the bits of dust and other debris which had become trapped in the drying sludge. They were thick, large stones in well fitted boxes, though, and based on the amount of wear they were showing must have been good stones, so I started looking into ways to clean them.
Although I had never thought of whetstones as having pores, the terminology I found being used was that a cleaning needed to “open the pores” rather than just removing the surface layer of dried sludge. To do that, it was recommended on several helpful websites to immerse the stones in a cleaning solution and then boil them for a period of time, or to use a more modern approach of putting them in the dishwasher for a few “heavy” cycles. There were a few caveats included that if you were not 100% confident in the strength of your relationship with those who share your household you might want to remember that the not-so-savory results of the cleaning process may well cake any pans or dishwashers involved with a fairly unappetizing (and probably unhealthy) scum.
Thus forewarned, I bought a disposable aluminum roasting pan, pounded the bottom as flat as possible to work well on my flat-top range, and decided to give stove-top boiling a try. I made a strong mixture of Dirtex cleanser and water with a little automotive degreaser added as an afterthought, put a layer of driveway gravel on the bottom of the pan to keep the whetstones from direct heat contact (which could crack them), placed the whetstones on top of the gravel, and filled the pan with enough solution to cover the whetstones.
I put the heat on high to get the solution steaming, then brought it up to a low boil at a lower setting since I wasn’t sure if it would foam up or not. It did, but not excessively so. After about 30 minutes the solution was noticeable darker but the stones still seemed covered in sludge, so I topped off the pan with some water and let it boil another half hour. At that point the stones still looked a little sludgy, so I took an old toothbrush and started lightly scrubbing the surfaces I could get to. That worked very well, and in a few minutes the stones had changed color to something looking more like a rock than an oil spill. Since I couldn’t get to the bottoms and didn’t want to put any of my kitchen tongs or other implements in the solution (which at this point was pretty ugly), I opted to let it keep boiling for another half hour and then turned off the heat and set the timer for 2 hours to let everything cool down slowly (again to avoid cracking the stones). At the end of the cool-down period I retrieved the stones and found their top surfaces looking free of oil but the bottom s slick and sludgy mess. A little scrubbing with the (now cool) solution and the toothbrush cleaned that portion off as well.
After letting the stones dry overnight, the next step was to check them for flatness. Both had been used so much that they were notably dished in the center, so a section of an old 80 grit sanding belt and my table saw surface were employed to flatten them. One was pretty soft and came flat quickly, but the other was hard and took about 20 minutes per side to wear down enough of the raised edges to be flat enough to use. A few passes over some 150 grit paper followed by a soap and water washing left me two good stones ready to get back to work.
What does this have to do with the purpose of this blog as a “gardening – centric” area of discussion? Not a huge amount, but the concept of opening the pores can also extend to a looking at a wider range of things than those initially considered. I am soon to head off on an extended business trip and have an idea that there may be some things worth blogging about that don’t quite fit within the gardening focus… so I am expanding the focus to fit.