Shop Talk
with Hans Durstling

The Coffee-Can Saw Oil Refinery

If the most disagreeable task in the lapidary shop is cleaning the slab saw perhaps the second in line after that is dealing with the old oil.

I used to put mine into a coffee can, where it then sat on the floor in the corner of the workshop, a malevolent slushy brown porridge of rock dust and Pella A, a disaster waiting to happen if somebody knocked it over. Yes it was covered with the plastic coffee can lid, but that didnít last long. Softened by contact with oil the lid within days would lose its rigidity and sag into the soup. After putting it off as long as possible Iíd finally buy a bag of kitty litter, mix it with the sludge (it took a lot! of kitty litter) and dispose the result in the domestic garbage which in my neck of the woods is still unsorted.

There had to be a better way. Iíd heard of filtering the sludge through a brown paper bag but did not at the moment have any at hand. The paper filter though seemed worth exploring, and the following adaptation is the result.

Step one is to provide yourself with the ubiquitous coffee can and denting tools in the form of a broomstick or similar.


Coffee can and denting tools.

Using the broomstick, dent out the bottom of the coffee can until it bulges. This concentrates the oil drip to the center of the can bottom and keeps it from running down the sides of the receptacle, which is simply a second coffee can of the same size placed underneath the filter can.

Step two is to punch a bunch of small holes into the dented bottom of the can. Use a scriber or any other sharp tool. If the bulge dents back inward in the course of hole punching simply use the broomstick to push it back the way it was.

Coffee can bottom dented so it bulges.

Punching the holes in.

And with the holes in, the filter holder is complete.

Step three is the manufacture of the paper filter. Place the coffee can on a piece of newspaper, draw the outline with magic marker or whatever comes to hand; cut out the disc with scissors. I used two thickness of newspaper. There is no scientific reason for this. Most likely three or four or just a single sheet would have done just as well, although I was worried that a single thickness only might rip, and hence used two.

Oil filter manufacturing - cut along the outline.

Then simply put the newspaper disc into the bottom of the dented can, weight it down with a few small junk rocks to keep it in place when you pour the sludge in, place the filter can on top of the receiver can Ė and voila, you have a fully functioning oil filter. I placed a few long strips of newspaper along the sides of the can to wick the oil down to the bottom, but I donít think this is necessary.

A two can stack and the backyard refinery is complete. For peace of mind you might want to run a bead of duct tape around the joint between the two cans.

Gently pour the sludge into the top can, and let the arrangement stand in a safe place. Within moments you will hear a slow drip-drip-drip sound, and within three days youíll have three or four cups of clear reusable oil in the receiver can, while the sludge in the top can that was initially as liquid as porridge will have compacted to about the consistency of clay, making it vastly easier to dispose of.

After three days standing. Clear oil in the receiver, compacted sludge in filter can, which, at the outset, was full to its brim.

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