What's not to like?
Lining them, that's what.
See, if you pour soap into a wooden mold without lining it, the soap can leak everywhere. And what doesn't leak out will be stuck like cement in the mold. And the lye will eat away at the wood, destroying the mold. And then you will go insane.
And so, to avoid going insane, it is necessary to line your mold with something. Most soapmakers go with freezer paper.
Freezer paper has a lot going for it: It is also sturdy, it's cheap, and it makes unmolding a breeze. Soap doesn't stick to freezer paper because the paper is coated on one side with plastic. (So make sure the freezer paper is shiny-side-up in your mold.) When it comes time to unmold the soap, just lift or slide it out of the mold, peel the paper away, and start cutting. (If you use a slab mold with dividers, you won't even need to cut the soap!)
What's not to like?
Making the liner, that's what.
The good news is that once you get the hang of making liners, it doesn't take that much extra time. And you can even make a bunch of liners ahead of time, like when you're sitting on the couch watching "Hell's Kitchen."
Here's even better news: It is possible to make a liner with one sheet of freezer paper. And the liner is totally leak-proof.
Here's how I do it. I found this technique in the book Basic Soapmaking: All the Skills and Tools You Need to Get Started by Elizabeth Letcavage and Patsy Buck. As I've mentioned, this is one of my favorite soapmaking books. It is full of color photos guiding the reader step-by-step through the soapmaking process and I highly recommend it, especially for folks who are just starting out with cold process soapmaking.
Basically, you need to find out both the length and the width of the bottom of your mold, and the height of the sides.Then you can measure out a sheet of freezer paper based on those dimensions. After that, you can figure out where you need to make your folds on your liner so that it fits perfectly inside the mold. It's not as difficult as it sounds. Trust me, if I can do it, you can do it, too.
It is far easier to show how to make a liner than it is to tell, so I made a video of the process. And you will finally get to hear me speak, if you've been waiting for that sort of thing. I normally don't talk in my videos because video editing is easier if I don't have to worry about maintaining a narrative. I can just chop up the video and add captions. Also, I don't really like the sound of my voice. Plus, I tend to babble like a psycho. Anyway, here's the video:
Here's a tip: Once you make a liner that fits, save it as a template. That way, when it comes time to make another liner, all you have to do is tear off a piece of freezer paper, lay it on top of your template, and trace the lines without having to figure everything out again. Big time saver.
Of course, there are ways around the freezer paper liner. I have heard of soapmakers making their own silicone liners for their molds so that they never have to make a liner again, but I am just not that handy. And I suppose you can buy silicone liners for specific molds or have one custom-made.
And if you don't want to mess around with liners at all, you can try an acrylic mold. I have an acrylic slab mold from Soap Making Resource that I love. And you don't have to line it, for reals. (Soap Making Resource also has acrylic log molds.)
Silicone molds are also great for soapmaking and they don't need liners either.
What do you all use? Have you made a silicone liner, or had one made for you? Or do you just use freezer paper? Do you line your mold with something else? Or have you made the switch to acrylic or silicone molds?