The number one question we receive on our bulk soap loaf site is, how do I cut the loaf of soap into bars? What do I use?
For years, we have used a wooden mitre box and a pastry scraper to cut the soap. If you choose to use a knife to cut with, make sure it is large enough to slice all the way through the loaf of soap — but, too large of a blade or too thick of a blade can cut away more soap than is needed.
If possible, invest in one of the better pastry scrapers, the kind with the firm or wooden handle attached. They also come as one piece of metal with a curve on the end for the handle, but this type tends to warp over time. They are, however, more affordable – usually only about $6.95. The better scrapers should run around $15 and up.
The reason we choose a wooden mitre box as a guide for cutting a soap is simple — it can be altered. Most mitre boxes do not have grooves that go all the way down to the floor of the mitre box. With a wooden model, you can insert a saw into the straight cut (you do not want to cut your soap on an angle for regular bars) and finish sawing the groove down to the floor of the mitre box. This insures that your bars of soap will be cut all the way through.
Now is the time to decide how wide you want your bars to be. Most people choose to cut their soaps into a one inch thickness. At Green Pergola, we cut our soap bars 1.25 inches thick, which gives us 12 bars from a loaf of soap. When you decide your thickness, measure over from the straight cut and make a mark on top of the mitre box to the right of the guide.
So, slide the soap loaf into the mitre box from the left and bring the edge of the soap over to the mark you’ve made on the top of the mitre box. Now, take your pastry scraper and start from the back side and begin sliding the blade into the soap loaf in a rocking down motion until the blade falls into the straight groove closest to you. You have now cut your first bar of soap off of your soap loaf. Repeat until finished. Any left over soap pieces, save for yourself or use as soap samples.