Making Reusable Mold Boxes

Why I'm Making Molds

           Several months ago I took a class from fellow sculptor Emily Coleman on silicone mold making. I chose to explore this process as I was toying with the idea of creating an art miniature line – which I ended up following through on.  It had become increasingly more important to me that I have a series of work at a variety of different price points; I wanted my work to be accessible to the widest number of audiences. Through this learning process and exploration of mold making techniques, I developed my own way of making a mold box.  And that’s what I’ll be going over today.  If you’re looking for more instruction – stay tuned. I have a video tutorial in the works.

The Way I was taught

          In Emily’s class,  she utilizes foam core for making mold boxes. She gets the large sheets and then cuts them down to size.  The sculptures she is creating molds of are bigger than mine are and this probably works best for how she uses this process in her studio practice. So far, my largest art mini is the giraffe, which measures just shy of 4″ at its longest edge.  Foam core tends to be firm and rigid – it’s what they use to mat posters/photographs/prints in a picture frame.  When I created my first mold box after taking her online course, I didn’t have foam core and used regular old cardboard which was mentioned as an alternative material. It worked okay. Essentially, you cut out a long strip (or 4 sides if you want to make a box) and wrap/form the foam core/cardboard into an oval/polygon that fits around what you’re making a mold of.  You need 0.25-0.5″ clearance between the edge of the item and the outer edge of your mold.  What I didn’t like was having to cut it down to size. And because it’s not flexible, every crease from every bend was visible in the cured silicone mold. I just didn’t like it, more of a personal preference thing.  THAT, and if I’m having any kind of hand weakness, cutting with scissors is difficult and using any kind of exacto/sharp knife isn’t always safe. So I worked on developing my own way of making a mold box.

Making a Mold Box - My Way

          My husband always jokes that I have more kitchen gadgets in my studio than we do in the kitchen…and to some degree he may be right. ha  My secret ingredient for my mold boxes….flexible cutting mats .  I had some laying around because they are a great material to make templates from – they don’t go soggy from the moisture in the clay AND they stand up to knicks from a pottery knife. I had some templates laying around that I wasn’t going to use anymore for its original purpose, so it became the sides for my mold box. I’ve been able to use this material for 3 more molds of sculptures of different sizes.  This method allows for total customization of the mold box shape.

Materials

  • Hot Glue Gun
  • 3-4 Glue Sticks (if they’re the small ones)
  • Painters/Masking Tape
  • Firm/Flat surface – I use a piece of balsa wood
  • Plastic Cutting Mat
Materials used for making a reusable mold box

Step 1

     The first step isn’t demonstrated, but it’s to have the flexible cutting mat cut into the right size and rough shape. I use a strip of plastic mat that is 5″ tall and about 12″ long. The bottom/base mat is roughly 6″ x 6″.

Step 2

Gluing a piece of plastic to a piece of balsa wood
Plastic glued to wood board

     The second step is to glue the piece of plastic mat that you are using as the base to the firm support structure – the piece of balsa wood in this case. All this does is help form a solid foundation so when you set it aside to allow the silicone to cure, nothing will shift on you.

     You don’t have to cover the wood with gobs of hot glue. I typically do a strip of glue at the top then zig-zag it down an inch at a time. I do it in sections like this so I can press the plastic down onto the wood to make sure there’s a good connection before the hot glue cools and hardens.

     See that black line down the middle of the plastic mat? There’s a reason for that.  Keep reading to find out what it is. 

Step 3

Small giraffe sculpted in plastalina clay
Hot glue on the bottom of a small sculpture of a giraffe

     The third step is to place the item you are making the mold of on the mold box base.  For this tutorial – I’m showing you how I made the mold box for my giraffe art miniature.

     This is where that black line down the center comes into play. You want to center your item as much as possible.  The line drawn in the center for the mold base should line up with the center of your item being molded – my giraffe for instance.

     Once you find the center, it’s time to glue the item down.  This is why I use hot glue for this process. It won’t damage MOST things that you want to mold (it hasn’t damaged anything that I’ve made a mold of, but one never knows..so I’m not going to claim it won’t damage what you’re trying to make a mold of.  If you’re unsure, feel free to email me and I’ll do my best to answer your questions)

Step 4

     Now that your item is secure on the base, you want to clean up that edge. My original art miniatures are sculpted in plastalina clay. So once the miniature is glued down, I take small slivers of clay and smooth it into the sculpture itself and onto the plastic mat. This creates a seal and will prevent any silicone from sneaking its way under the sculpture.  If this happens, it’s not a big deal, just takes a bit longer to clean up the mold at the end…. but that is a whole ‘nother tutorial for another day. 

Step 5

small clay giraffe sculpture with wire supports

     This is another step not fully demonstrated here. But due to the shape of this mold, I added some pieces of wire that will create air vents to the nooks and crannies where air bubbles are likely to get trapped. The air bubbles don’t happen in the mold making steps, but later down the road when you’re using your mold to make your castings/reproductions.

Step 6

     Now that long piece of plastic mat that we haven’t used yet?  It’s time to grab that and form it into an oval.  If the ends overlap – perfect! Once you have the rough shape formed, you are going to tape the edges on both the inside and the outside of the form. If you look closely, you should be able to see that there is roughly 0.25″ clearance all the way around the item being molded. That’s the minimum amount of clearance you want for this process.

Step 7

     Once you have your oval, it gets a tad tricky.  As such, I don’t have pictures for this part (another reason why I’m creating a more in-depth class for this process). In your non dominate hand, hold the walls – the oval you just made – in place around the item you are making the mold of. With your dominate hand, you are going to use your hot glue gun and glue the mold wall to the base. The wall should be flush against the base.  You are gluing the outside of the wall. This is where most of the hot glue gets used. I use at least 2 glue stick on this part alone.

Step 8

     The last step in the mold box making part of this whole process, is to place a piece of tape across the top of the oval. It doesn’t have to be tight. This is simply helping keep the shape of the mold box when it comes time to pour the silicone in.

De-Molding

        The “reusable” aspect of this mold box comes at the very end of the entire mold making process. At that point you’ve theoretically mixed and poured the silicone in, let it set up and cure for 16-24 hours, and now it’s time to “de-mold”. In the original method, the cardboard and foam core are easily destroyed. By using the plastic mats, all you have to do is peel off the tape and the hot glue and then remove the plastic from the silicone. It comes off VERY easily. Set the plastic mat aside for the next time you have to make a mold. The hard part is in the de-molding when you’re cutting into the silicone.

Conclusion

     If you’re familiar with the mold making process, I hope that this quick abridged tutorial made sense and you are able to try it for yourself.  If you’ve never made a silicone mold, I readily admit that some of these steps might be a tad confusing. But I do hope I’ve planted a seed of interest that you explore further. As I’ve mentioned before, a video class is in the works for this entire process from start to finish – including the mixing of the silicone!

      Do you make silicone molds? Or are you plaster mold kind of person? I’d love to know what you thought about this tutorial regardless of your experience level!

     Shawna is a ceramic sculptor and mixed media artist who loves sharing her passion with others. She is a teaching artist and a strong advocate for the arts being accessible to all. Check out her Patreon page HERE for exclusive content, sculpting tips and fun times!

     Some links in this post are affiliate links. I may earn up to 10% commission for any purchases of the products linked to. Please be confident in knowing I will only link to/promote products I actually use and recommend. Several of the links are to products found on Amazon, so if you use smile . amazon . com , you also get to help your favorite charity. My purchases from Amazon help support the Travis Mills Foundation.

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