Same here. It's the cheapest mold I've found but you can only use it once.
Milk cartons are covered with wax or a waxy substance to make them water proof. It also makes them soap proof, almost like having a wax paper lining built in.
I'm saving all milk and juice containers now, for use in test batches. And best of all, you just fill them up to whatever level you like. They're fairly flexible as far as batch size goes, particularly if you keep several on hand for overflow.
The only negative is that the 2-3/4" x 2-3/4" square bars are less than ideal as far as shape and the edges will be rounded and somewhat bowed, negative if you want them straight, or no big deal if you don't care. I taped a metal "L" shaped bracket to the sides to avoid parallelogram distortion in the shape. You can get one at a hardware store for less than a dollar.
A one quart milk carton has a volume of 58 cubic inches and accepts a batch made with 23 ounces of oils. It will produce about 6-8 bars 1" thick. That'll save you the calculations.
Let me point out that you can double the amount of oils and use two milk cartons. That'll give you a batch size of about 3 pounds (46 oz). That's a pretty nice batch size although 1-1/2 pounds is nice too.
Oh a bit of a tip: You might want to have a large funnel handy.
Others have been very helpful to me. I can't help them back because they are experts who don't need my help, so I can at least pass it along and help those less experienced soapers. You'll be up and running in no time and I'm sure you'll be helping newbies then.
I think you'll progress rapidly because you're so enthusiastic about making batches frequently. You learn something from each batch. Make 12 batches in a month and you'll progress from newbie to intermediate in a month. Make 12 batches in a year and you'll progress from newbie to intermediate in a year.
I think you're dead set on making 12 batches in your first 10 days!
That is an excellent tip about the L bracket. I use milk and cream cartons all the time but I don't like that distortion. The funnel sounds useful too especially if the trace is light. I had trouble getting gel from the cartons so I used to just stick them in the fridge and forget about gel. Now I have a nifty little solution to the gel problem. I make a little nest of small towels in a big pot and I set the filled carton in the middle of the nest and cover over the whole thing with a blanket. Works great. Also, I don't like those square bars that you get from the carton, so I cut them in half and this size fits well in my hand .
Hiya Rita! The funnel is useful because it's difficult to pour into the relatively small mouth of the milk carton. I have a ladle but using it would be laborious.
I placed some old towels in a cardboard box I had laying around, then put the milk carton on that in the center of the box, then stuffed in wadded towels around the carton on all sides, and finally covered with another layer of folded towels. I got noticeably exothermic temperature rises and excellent gel using this technique. I've been playing with using a remote reading roast thermometer and digital readout to monitor the gelling of some batches. It's interesting even if not useful.
I have cut milk carton bars in patterns other than the obvious 1" thick slices and gotten somewhat more pleasing form factors. You could for example get 2-3/4" x 9/10" x 3-1/2 (or so) going vertically. I'm sure there are more perhaps better choices. The rounded corners and bowed edges are always a problem unless you trim but then you waste part of the soap.
Yes, I cut the tops off too, but it's still difficult to pour from my soap pot into the carton because the pour width wants to be wider than the mouth of the cut down milk carton. A large funnel neatly solved the problem.