Impresa Premium Glass Cutting Oil with Precision Application Top - 4 Ounces - Custom-Formulated for an Array of Glass Cutters and Glass Cutting Applications - by Impresa Products

That is not optional if you want a clean cut. Works really good.

Not sure if the quality of the oil or quality of the knife is the most important but regardless, people recommend to use oil to lubricate the knife when cutting glass so that's what I did. Didn't face any issue.

Facile à utiliser Donne de très bons résultats

I am new to stained glass and was struggling to cut my glass easily without breaking my glass incorrectly. This oil is a game changer. It’s easy to use. It’s a big bottle so it will last you a long time. Since using this my glass cutting is now flawless. I highly recommend.

I used it to cut a huge mirror for the wife and it worked but it could be a bit thinner or it might have been my glass cutter wasn't dispensing the oil enough. Either way it cut the mirror. The cap did break when I was tightening it