Making a Two-Step Silicone Soap Mold, Part Three

They have an amazing number of raw casting products. For soap molds, I use the recommended silicone, which is Soft 107, and it can be found  here.

I can't say enough good stuff about this online store. They are super nice, and have a lot of resources on their site. They even answered my silly questions quickly!




First, you need to do what I consider to be an obscene amount of math for an artist. Luckily for this kind of mold, it's not calculus. Even calling it algebra is a stretch. It's mostly proportions, which I learned about when I was first taught to sew as a tot. Doing that kind of math stuck with me, and I use it everyday when doing production art at work, or when painting or soaping. Hobby Silicone has very general and extremely accurate instructions for figuring out how much silicone your mold will need, which can be found here.
(I convert the pounds needed to ounces because that is what I am used to working in.) 
If you just want to make one mold, you may not need to do the math for how much silicone you'll need before you make your Two-Step mold (the mold with the foam board and the "part").  HOWEVER, you MUST do the math before you buy your silicone.

I generally tend to do all of the math before I even make the Two-Step mold, so that I know what I am getting into before I start spending money on anything, even the foam board. 

DO YOUR MATH & CHECK IT, TOO! 
TWICE.  AT LEAST.



This is the 10# kit for Soft 107, which is what is recommended for soaping molds. The larger container is the base, and the smaller is the catalyst. This particular one is mixed in a 10:1 ratio, 10 parts Base to 1 part Catalyst.  I got VERY lucky, again, when calculating the silicone needed for these three molds - it wound up being 9.9 lbs.  Yay!




Just a close up of the labels. 



Get your work station ready.
You can use the same scale you use for soaping. Otherwise, you'll need some method of accurately measuring the two parts. 
Wear gloves, getting this stuff on your hands is not fun. It's not dangerous, but sticky and messy, like marshmallow creme or hot taffy. I buy my gloves at a beauty supply store. A large package of hair coloring gloves is not too costly and you don't feel as bad tossing them out after. I use them while soaping, too. 



Set your Two-Step mold(s) somewhere it can rest undisturbed for 24 hours after the pour, while the silicone cures. Have room to work comfortably. Place it over several layers of newspaper or newsprint - just in case it leaks. 



Before pouring, check to make sure your mold is as level as you can get it! This is also your last opportunity to check the surface of your mold for dirt, debris, scratches, etc. Once poured & curing, you can't take that silicone back, so if the image is marred in any way, any defect will end up being part of your mold. 



You need a container to mix the silicone in, and a utensil to stir it with. A plastic container that you are not in love with is best. For this, I'm using the Base container from my last kit, because I'd just be recycling it anyway. The spoon is just a cheapie long plastic cooking spoon, like what you'd use for a stir fry, that I got just to do this.



Put on your gloves. Have your calculations handy - I taped mine to the cupboards in front of me. (The last thing you want is to be in the middle of pouring your raw materials, then forget the quantities, and then have to put things down and go searching for your recipe!!! Augh!) Measure out the base (the sticky white stuff in the large container). Measure & add the catalyst to the base (the liquidy purple stuff in the smaller container).



Start stirring baby! Don't stop until the catalyst is fully incorporated into the base and the color is uniform. In the case of Soft 107, it will be an almost fluorescent lavender - very pretty, actually



Take the silicone to your mold. Start your pour by aiming the stream for ONE corner and staying there. It will go where it needs to go on it's own, and by staying put in one place you help reduce the likelihood of bubbles or air gaps and allow the product to creep in slowly the way it wants to. Don't panic and try to dump it in, you still have plenty of time to pour at an even pace before it begins to set up. 



Once filled, it should reach the intended height if you did your math right. What you are looking at right now is actually the underside or base of your mold. You don't want to run short on your mixed silicone and have a thin base - it could rip easily and/or will not be very stable for the soap.  So - like I keep saying - DO YOUR MATH BEFOREHAND.  



I had a small leak in my main 25-bar mold, the big mold. This happened last time as well - remember the silicone expands just a bit and it goes everywhere it can - every crack & crevice. There's no need to panic unless you have a gaping hole. You can see how it pushed out to a certain point over a few minutes, and then just stopped. 



One thing I learned this time out was to use better glue sticks. I ran out of them after making that first Two-Step mold up there with the leak. I decided to upgrade to a better glue gun that would use the longer sticks (which is not as much of a pain because they don't run out as fast, and you can get a longer bead). So off I went to the craft store and braved the small, loud, running children and their indulgent parents. When I made the next two molds, I found out the new glue was of much better quality - because as you can see, they didn't leak at all!!  Not bad for a $12 investment. 




There they are - all three molds filled to the levels as expected with the math. You can see in the image below that I marked an arrow at the expected height - the main mold on the left is for 25 full-size bars and therefore much taller than the "special effects" molds. 

 I was also very, very happy, as I used up the entire kit and didn't need any more beyond that. I just got lucky this time!  



And here they will sit, undisturbed, for 24 hours. 


Next:  Un-molding the silicone and making a frame for your mold.