How I Made My Own Slump Molds

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How I Made My Own Slump Molds

Living in the County of Glengarry, my home and studio are only a short drive to Maxville, Ontario, home to the largest Highland Games in North America. You can imagine the honour I felt when commissioned to design and create special awards that some of their elite athletes would take home.

After meeting with organizers on a few occasions and creating a few sample pieces, they decided that they would like to go ahead with the project. I was to make 9 inch and 6 inch plates of the same design changing only one of the glass colours.

Simple right?

Here Was The Challenge

You see, I have this wavy plate mold that I bought used from a woman selling off her studio a few years back. It’s one of my favourites and it turned out to be one that the organizers loved too.

The mold itself had no markings and I had no idea where it came from or which company made it. I searched online for it and couldn’t find anything similar so I took photos and sent them to all of my suppliers seeing if perhaps they could identify it or procure one for me that was the same style.

As it turned out, no one could.

I was told by the organizers that the smaller plates didn’t have to be identical in shape to the larger ones and that something very similar would be fine. It’s at this point I agreed to take on the commission.

My husband and I had discussed mold making techniques year ago, and since then, I had come across other materials and ways of making molds for glass fusing.

How hard could it be? (Famous last words!)

If you’ve ever been in this situation, I bet you’re shaking your head at me for being so naive. And deservedly so!

Despite having played with clay for mold making unsuccessfully years ago, I was confident that my learned knowledge since then would make it much easier now, as I didn’t plan to use clay at all.

This post contains affiliate links, meaning, I recommend products and services I’ve used or know well and may receive a commission if you purchase them using my link (at no additional cost to you.)

First Attempt with 1/2 fiberboard

After conducting further research online, I discovered that fiber products might prove to be the easiest materials to use in making the small molds I needed. I already had some ½ inch thick fiberboard so I got started on my first attempt at making my own mold. I carved and cut away the fiberboard using a small utility knife.

In order to keep the bottom of the plate flat and level, I thought that if I carved the fiberboard all the way through, the kiln shelf would provide the best surface to help me achieve that. The problem was that I couldn’t get the inner edges to taper enough without tearing while cutting it.

Secondly, (and this didn’t even occur to me at the time) there would have been no way to allow trapped air to escape. This is why slumping molds usually have a hole or two in the bottom. It’s to allow air out so that it doesn’t cause the glass to puff up from trapped air creating a bubble underneath it.

In the end, I wasn’t happy with it and felt that the fiberboard wasn’t quite thick enough to provide enough depth to the design this way. So I moved on to my second attempt.

Second Attempt with 1/2" Fiberboard

I discussed the next best approach with my husband. (He’s my sounding board for many of my ideas, especially those that require some technical knowledge.) His suggestion, was to carve the fiberboard in such way that instead of slumping the glass into it, it would drape over it instead.

I was on board.

It sounded like a much easier way to carve the fiberboard and I figured this would do the trick! So I set myself to work.

I cut and carved away the excess material still using the ½ inch fiberboard. But I realized part way through, that if I were to drape the glass over this form I was making, the inside of the plate would not end up having that smooth, polished finish.

This was no good!

I was stumped. How was I going to make this mold?

Did I mention, that in order to complete the order efficiently, I was actually going to need 3 of these molds?

Stress set in. I had already committed myself to this order and I would need to figure out a solution quickly, to ensure that all the plates would be ready for their due date.

Making a Mold with Fiber Blanket

Have you ever heard of fiber blanket? It’s another fiber product that can be used in the kilns. It reminds me very much of super thick quilt batting.

My ingenuity got me excited. I knew the solution!

I would order some 1" thick fiber blanket and a 16 oz bottle of rigidizer (also known as mold hardener.) The rigidizer does exactly as the name suggests. When applied to the fiber blanket and fired, it causes the blanket to go hard and hold it's shape. 

I had never used fiber board for anything other than a shelf for fast firing and cooling and I had never used rigidizer or fiber blanket before either. So I turned to the internet in search of more information.

Unfortunately, all I found was that when using the fiber blanket, if you wanted to shape it, you used rigidizer.

Well that’s all fine and dandy, but nowhere could I find any explicit instructions on how to use it or apply it and there were no instructions on the bottle that I had.

“No biggie” I thought “I’ll play a little and figure it out.”

My plan was to use the mold I had carved for draping in my second attempt to shape the fiber blanket. ​I would add the rigidizer to the blanket and lay it over the raised form while firing it. This would allow the edges to drape beyond the ½ inch thickness of the fiberboard. Then once fired, it could be turned upright and used as a slumping mold instead of draping as I had been thinking in my second attempt.

I started by squirting the rigidizer out of the bottle straight onto the fiber blanket thinking I could spread it around after, but the blanket was so absorbent it soaked it up before I had the chance to spread it with a paint brush. I ended up pouring it onto one of my plastic trays and allowing the blanket to soak it up.

Then I carefully placed the rigidizer soaked fiber blanket on top of the mold from attempt number two, which was raised on top of attempt number one to give it a little more height off the shelf.

I fired it overnight.

Excited at the prospect of having a finished mold, I opened the kiln the next morning to see what was waiting for me. I peeked in and it looked great!

It did just what I thought it would. That is, until I tried to remove the blanket from the board.

They had fused together!

The blanket mold was destroyed when I tried to separate the two. And to make matters worse, the mold from my very first attempt, which was on the very bottom of the stack, partially fused to the shelf.

If only I had put a piece of shelf paper between the fiber products, I could have separated them without any trouble. Even still, I had used half of the bottle of rigidizer and the blanket came out of the firing with a hardened shell, but it certainly wasnt solid the whole way through. My guess is that it wouldn’t have lasted as a mold anyhow.

I was so frustrated and stressed at this point. I wondered how on earth was I ever going to make these molds?

Four days of failed attempts and I was no further ahead. I had no idea how I was going to do this.

A little more pondering brought me back to my first idea of carving a slumping mold in fiberboard but it would have to be much thicker than before.​

Carving 1" thick Fiberboard

I got my hands on some 1 inch thick fiberboard and decided I would just have to carve the mold as I did in my first attempt but not go all the way through the bottom. It would be kind of risky though as I had to make the sure the bottom would be flat enough to create a plate that didn’t rock on a table.

I started carving.

I carved slowly and approached each new section with a lot of pondering. After a couple of hours, I had a shape that I was content with. I made a hole in the bottom and applied the rigidizer, and set it to fire overnight.

Would this be it?

I was hopeful but didn’t want to get overly excited. After all, I was completely out of ideas. If this didn’t work, what on earth was I going to do?

Upon inspection the following day, I was delighted to find that this mold was the first of three I would create that would in fact suit my needs. I did a test fire with a 6mm clear glass and it turned out wonderfully! I fired it too hot and it picked up some texture from the mold, but that was easily ​fixed by adjusting the firing schedule for my custom plates.

I carved two more the same as the first. Each one got a little easier to make and a whole lot quicker too.

I’m so glad that I stuck with it. How rewarding it was to see all the plates finished successfully with time to spare.

As creators, we either have a strong belief that we can do something or we doubt ourselves all the way to the bank. I learned a lot from taking on this commission and I'll share the two I found to be most important.

​Lesson #1

Creativity isn’t just about creating.

Don’t get me wrong, it is a huge asset when creating art, but I really think it boils down to a way of thinking. It’s about having a curious mind to explore different concepts and helping or causing ideas to evolve. And it also about having faith in yourself when it comes to finding solutions to your problems.

Sometimes you have to work at it, and other times the ideas just flow.

​Lesson #2

Perseverance will take you further than you ever imagined.

There’s a quote from motivational speaker Josh Shipp which says “Perseverance is stubborness with a purpose.” I believe this describes it perfectly.

And I’m sure if you asked my loved ones, they would attest to the fact that I can be (just a bit) stubborn at times.

​In Conclusion

My advice for you? Be stubborn and don’t give up. There is probably a way to do what you’re trying to, even if you haven’t found the solution yet.

If you've read this whole post, you'll know that I was disappointed at not finding a step by step on how to work with rigidizer and fiberboard and yet I haven't given any specifics on how to do it here. But don't fret! I've made a free step by step tutorial for you.

See the tutorial here: How to Make a Mold from Fiberboard

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About the Author

Samantha's a passionate creative with varied artistic interests which she loves to incorporate into her glasswork. Working in both stained glass and fused glass, her goal is to help you be creative and think outside the box while teaching skills to make glass crafting easier.

Samantha Calder

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    1. And thanks to you for the hardener! It made moving forward with my project possible.

  1. Even with the tutorual- I would be very nervous about the 4 sides not being exactly the same curvature….I am very impressed with your work . Any additional tips are welcome.

    1. Thank you. I do understand your concern, Terri. I was so afraid of that happening and that’s why I created the templates to help me. Given that they are hand-carved, there is always the chance that something may be off a little but that’s part of the joy of handmade items for many people.

  2. Hi, I love them. Thanks for sharing your ups and downs. I love the scottish thistle do you mind sharing how you did the gold thistle.

  3. Thank you so much for sharing your process! If I may ask, how did you finally apply the rigidizer in your successful final attempt? I’ve got supplies en route, but still don’t really know.

    1. I ended up soaking the piece in rigidizer and allowing it to absorb a good amount of it. Be careful doing this that when you lift out the fiberboard, not to crush or dent it where you’re handling it. Worked like a charm!

  4. This was very informative. You are very talented. Thanks for sharing.

  5. Thanks for the detailed and informatice tutorial. Moulds are a constant pain if you just do it as a hobby as they are so expensive. I tried pottery clay but found they cracked as I think they had different expansion rates (or just me.) Currently trying stainless moulds and plan to approach a metal fabricator to see if they can shape them. Got some really cheap ferrous ones used in the building industry from the hardware store and they worked quite well once coated.

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