The Why and What of Kerosene As A Cutter Lube

One of the things we get worked up about is all the misinformation about glass cutter lubricants. So much so that we feel compelled to rerun this blog entry;

It was a Canadian who discovered kerosene and invented the kerosene lamp. Dr. Abraham Gesner showed off his invention in 1846 on Prince Edward Island (how do you think he figured out where he was? He could finally see the map). He named it by putting the Greek word for wax, keros with the shape of his belly button, ene (not an oute).

Dad said you really never learn to swear until you learn to drive. That's not true- it's when cutting glass with the wrong lubricant. Yes folks, it's true- the type and the quality of lubrication is critical to successful glass cutting.
Now, a bit of a discussion as to why you want to use kerosene and nothing else as a cutter lube:

Glass is a strange material- it's not a solid, or a liquid, but a vitreous solution- something exhibiting traits of both and none of either- oh, never mind, just read FigHelper # 7 for an explanation, we must move on. The only thing you need to concern yourself with for the purpose of this discussion here is that the outside skin of glass is in a state of 'tension' (sort of like Mikey's home right now…), holding the middle in 'compression'. 
When making a score with your glass cutter, the wheel only penetrates the surface of the glass by a mere 1/1000th of an inch (less than that in centimeters…helpful Ed), into the area of tension, but, at the same time it drives a crack well into the deeper compression layer. Using a lubricant will minimize excess surface fractures as your wheel rolls along the glass. A lubricant literally 'oils' the score line reducing surface damage, and as a bonus it reduces the tendency of the score to heal itself (that's Earnest Ainsley's job). The lubricant best suited to this job? Kerosene of course!

Now, while you might be a better person for understanding the principle behind making a score, you're not really any closer to finding out why we want you to use kerosene. After all, why put oil (which kerosene is) on glass that's already clean? This means we'll have to clean the glass before copper foiling people tend to whine. 
Oh, the horror. Hey, if we analyze the purpose of a lubricant we could theoretically use any liquid (don't go there Ed). After all, it's the presence of a liquid that's important, not the type. Sounds kind of like Deja Moo- the feeling that you've heard this bull before.

But why kerosene? Let me illustrate the ways;
1) Well, most importantly it is a liquid.
2) It "facilitates the smoothest penetration of the glass surface, keeping microscopic chipping to a minimum" according to the experts.
3) It's cheap and widely available.
4) Its oil base protects cutters from corrosion unlike many of the synthetic cutter lubricants that make unscrupulous retailers lots of money
5) It evaporates almost totally, leaving little residue.

6) It is not sticky, and will not thicken in viscosity over time therefore it won't clog up the wetting wick in your cutter.

Let's expand a bit here and discuss the cutter wheel doing all the work. The angle to which the wheel edge is ground is the hone angle. This is an important factor in determining how well the wheel can have and then hold a sharp point. Getting it right with steel is very difficult, as steel does not allow itself to be well sharpened and then almost impossible to keep sharp. To compensate, manufacturers steepen the hone angle to compensate for steel's weakness. Stained glass cutters with steel wheels average 114- 120 degrees hone angle. The ubiquitous Toyo Supercutter's tungsten carbide wheel uses a wide (135 degree) hone angle with a very sharp point.

Now what does all this highly technical talk about hone angles have to do with cutting glass. Well, it seems that the difference in impact between a steel wheeled (steeper angle- blunt point) cutter and a tungsten carbide (shallow angle- sharp point) one is sort of like dancing with a 250 pound man in open toed (but with wool socks) sandals or with a woman wearing an off the shoulder chiffon red dress and matching stiletto heels. The pressure applied to the glass is directly proportional to the amount of wheel touching the surface of the glass. This is one of the reasons carbide wheels regularly outlast steel by 50-1.

That is all.