After a good deal of experimenting, and observing other people’s methods on the Internet, I’ve settled into a routine method for cutting and breaking glass bottles that really works well for me. I guess it’s about finding your own preferred method, but some of the well publicised ones , to me at least, leave a lot to be desired, and the results demonstrated speak for themselves. In this post, I hope to break down the steps I take to demonstrate my best method of cutting bottles, which is one I regularly get around 80%+ success rate with. Though not as demonstrative as a video, the photos and blog post should hopefully still be useful to follow my own chosen technique, which has worked very consistently over several hundred of cut bottles so far.
The first step to cutting a bottle successfully is the most obvious, but often the most overlooked in terms of a prime reason why the bottle cutting fails. There are some methods of breaking a glass bottle using heat from an acetone-soaked string line, or an electric current, or even hot oil inside the bottle, but most demonstrated results are often quite poor. I only use, and recommend, the traditional glass scoring technique, using a glass or dedicated bottle cutter. This helps to create a consistent and clean score line which should run well if performed correctly. This is the key stage to a successful cut in my opinion. A singular, light, clean and unbroken score line is essential, and, beginners to the hobby might be tempted to have a heavy score line to feel they are breaking into the glass. Heavy scorelines, that leave lots of flakes are the most likely to crack and run off when breaking commences. A consistent, gentle pressure with the two ends meeting is what you need. Ensure your wheel is lightly oiled, and don’t go over the same scoreline twice. You want a nice, clean scoreline as the photo right. Without this clean start, the odds of a poor break are magnified.
When it comes to the breaking, I’ve settled on the hot and cold water method observed on YouTube, with reliable and good results right from day one. The Ephrem’s cutter comes with a candle to use in conjunction with a block of ice, but I found that technique very unsatisfactory. It was messy, slow and gave poor results. I much prefer to use a pouring kettle, and a cold running tap. Depending on the thickness of the glass (thinner glass go slightly cooler), I use the kettle just “off the boil” (around the 70-80 degrees Celsius mark, though I don’t use a thermometer). Using a kettle means you can pour a neat line of water just over the score area, without letting it spread too widely across the body of the bottle, which I find helps a great deal. My preferred method is to use a sink bowl for balancing the bottle, and rotate the bottle around a few revolutions, pouring the hot water over the score as i rotate slowly. I used to try creeping the cut by flashing a section with hot water and immediately quenching it under the cold, but this isn’t as consistent as a full score heating by several turns. When I gauge the bottle to be hot enough after three or four turns, I then rotate the score under a slowly running cold tap, turning it fully to quench it as quickly and uniformly as possible. This should give you a clearly visible fracture line all the way around the bottle, as photographed to the right. When you have this look all the way around, without any runs, you know you’ve got it sussed.
A second, gentle pour with some hot water is usually enough to separate it fully at this stage, and the two parts completely separate without any human touch required, leaving clean edges ready for smoothing. No bottle will be completely flat when separated, but this technique gives you consistently very straight edges as the photo to the left shows, which are straight-forward to finish (see my preferred method in the post edge finishing) . I’ve used it on thin beer bottles, small condiment bottles, wine bottles and very thick whisky bottles all to a good standard. It’s by far the best way I’ve come across so far, regardless of which bottle cutter you initially use.