How to Make a Box with Scrap Polymer Clay
If your scrap polymer clay stash is taking over like mine, it’s time to put it to good use. In this tutorial, I’ll show you how to turn those questionable scraps into something functional and fabulous—a custom polymer clay box.
This is Part 1 of a two-part series. Here, you’ll learn how to build a sturdy box and snug-fitting lid using scrap polymer clay and a glass jar rescued from your recycling bin. Whether you’re new to clay or an experienced maker, if you love giving scraps new life, you’re in the right place.
Why Make a Polymer Clay Box?
I’ll be honest, looking at my bin full of scrap clay can be annoying. When colors blend nicely, great. When they don’t? It’s just a pile of mud. A never ending pile.
That’s why I love covering scrap-built boxes with pretty veneers. Once you decorate your scrap polymer clay box, it becomes a perfect holder for trinkets, jewelry, or even doubles as eye-catching decor.
The best part? It’s completely up to you and how you want to make it fit your vibe. Go bold and bright, or keep it neutral and chic, it’s your call. I’ve covered mine in mica shift, mokume gane, and cane veneers before, and loved each one.
Choosing Your Mold: Peanut Butter Jars, Glass Bottles, and More
Your mold can be as humble as a peanut butter jar or as fancy as a metal food ring. Either way, straight sides are a must — flared bases make sliding the clay off the mold impossible.
For this tutorial, I used a glass peanut butter jar but you can also see the boxes I’ve made using a glass bottle and a metal food ring.
The jars were the easiest, I baked the lid and base rings at the same time. The oval shape from the food ring was cute, but a bit more work since I had to bake the pieces separately.
Mold prep tip:
You can work directly on glass or metal, but trust me, wrap it in paper first. Copy paper taped snugly around the mold makes removing the clay much easier. I learned this the hard way (sweat and swearing included).
Conditioning and Prepping Scrap Clay
Time to raid that scrap bin.
Condition your clay. Mix brands, mix colors, and don’t worry about the lint and stray cat hairs. Older, firmer clay actually works better here.
Don’t love the color? Try this:
- Paint the inside later before adding a veneer. Acrylic paint works great.
- Add Kato Blackout. I used 10% by weight to darken my weird muddy green into a nice charcoal.
- Use fresh clay for the interior. More on this while still using up some scrap clay in the variations section.
Ready? Let’s make some DIY clay boxes!
Tools & Materials
- Non-porous work surface — I work on either glazed tile or glass
- Pasta machine dedicated to polymer clay use — I use an Atlas 180 and will refer to the settings I use on my machine. If you don’t have a pasta machine an acrylic roller and some playing cards will do in a pinch, it’ll just take a little more work.
- Scrap polymer clay
- Clean glass jar with straight sides
- Copy paper & tape
- Craft knife and / or polymer clay blade
- Ruler
- Glazed tile for baking
- Liquid polymer clay
- Sheetrock sanding screen or sanding block
- Silicone tipped tool — optional but nice to have for blending seams
Directions for Scrap Polymer Clay Box
1. Condition and Sheet the Clay
First, grab your scrap clay and start conditioning. You can blend the colors until they become a single, unified shade or stop while you still have some interesting marbling. It’s up to you.
I had a lot of black in my scrap pile and my blend ended up a murky green (it didn’t show up well in photos, but trust me, not cute). To fix that, I added about 10% Kato Blackout by weight, which darkened the clay to a nice deep charcoal. However, adding Blackout does soften the clay quite a bit, so keep that in mind. Mine was softer than I’d like, but still worked just fine.
Once conditioned, sheet the clay through your pasta machine on the thickest setting and set it aside.
2. Prepare the Mold
Next, get your mold ready. In this case, a clean jar with straight sides works perfectly.
Cut a sheet of copy paper to size and wrap it tightly around the jar, taping the end in place. This step makes removing the baked clay much easier later on. Yes, you can skip the paper and work directly on glass or metal, but speaking from experience you’ll probably regret it. In my experience, wrestling baked clay off a naked mold is… let’s say “character-building.”
3. Cut and Wrap the Clay
Measure the circumference of your jar. Then trim your sheeted clay to match that length. You’ll need two strips: one for the box base and one for the lid.
For this tutorial, I cut my lid strip at ½” tall and the base strip at 1½”. You can adjust these depending on how tall or shallow you want your box to be.
Wrap each strip around the jar, keeping them as straight and even as possible. Where the ends meet, smooth the seams with your fingers or a silicone-tipped tool. Take your time — the neater the seams, the better the final result.
4. Bake the Rings
Bake the wrapped strips directly on the jar at the recommended temperature for your brand of clay for 45 minutes.
If you’ve mixed brands (which can happen when working with scrap), bake at the highest temperature recommended. Don’t worry about minor discoloration here — strength matters more at this stage, and higher temps will make your box sturdier.
Once baked, let them cool completely before moving on.
5. Sand the Edges
When cool, carefully remove the baked rings from the mold. Sand one edge of both the lid and base until perfectly flat. This step is key to ensuring the next pieces bond seamlessly.
A sheetrock sanding screen or a sanding block works well here. You want a nice even edge that will sit flush against the clay you’ll be adding next.
6. Create the Box Base and Lid Top
Sheet more scrap clay on the thickest setting and burnish it onto a glazed tile. Avoid trapping air bubbles.
Note: In the photos, you may notice I burnished my clay onto a sheet of paper. I find this can help avoid air pockets, but you’ll need to peel the paper away while the clay is still hot from the oven, otherwise, it sticks and may cause warping as the clay cools. Try it if you want, but be prepared to work quickly and carefully.
Apply a thin layer of liquid polymer clay to the sanded edges of the lid and base. Press them down onto the sheeted clay. Let them sit for a few minutes to bond.
Once set, trim the excess clay. I like to slide my blade straight down the side of the box for a clean edge. I also flip the blade over and use the dull side to gently smooth out any leftover clay for a neater finish.
Bake again for 30 to 45 minutes.
7. Build the Lid’s Inner Collar
After baking, sand the open edge of the lid ring so it’s flat and even.
Sheet more scrap clay on a medium-thick setting (setting 2 on my pasta machine). Cut a long strip about ¼” wider than your lid ring height. For example, if your lid ring is ½” tall, cut your strip ¾” wide.
Apply liquid clay to the inside edge of the lid and gently press the strip into place inside the lid to create an inner collar. This helps the lid fit snugly over the box base without sliding around. Use your fingers and/or a silicone tipped tool to smooth the seam. Make sure the strip doesn’t flare outwards, this will make fitting the lid onto the box tricky later on.
Once everything is smoothed and in place, bake the lid again for 30 to 45 minutes.
8. Fit the Lid and Finish the Box
While the lid is still warm from the oven (but cool enough to handle safely, remember, hot clay is fragile), gently place it onto the box base. This helps ensure a snug fit as it cools.
Once completely cool, sand the entire outside of the box to smooth any rough spots and prepare it for your final veneer.
Creative Variations and Ideas
- Vary box heights for a decorative set.
- Try different jars or bottles for unique shapes.
- Use metal cutters with deep sides for fun geometric molds.
- Use fresh clay inside and veneer outside for color coordination.
How to Add a Coordinated Interior (Optional Step)
Still want to use up your scrap clay but create a coordinated interior? Here’s how to do both.
Roll out a sheet of scrap clay on the thickest setting. Cut it so it’s tall enough to for the height of your box and about an inch longer than half the circumference of your mold.
Next, cut a straight line through the sheet to divide it into two strips — one for the lid and one for the base.
Take a strip of fresh clay, rolled to the same thickness as your scrap clay. It should be about ½” to 1” wide. Insert this between the two scrap strips and burnish the seams to bond them together.
Now, roll out another sheet of fresh clay on the thickest setting and cut it to match the size of your scrap clay sheet.
Layer the fresh clay on top of the scrap clay and run them through your pasta machine on the thickest setting. Make sure to feed the clay through in the same direction as the arrows in the diagram (you want to make the sheet longer, to wrap the mold, not taller).
Finally, cut along the fresh clay inset to separate the lid strip from the base strip. Wrap your mold just as you did before, making sure the fresh clay faces inward. This will give your box a coordinated interior while using up plenty of scraps in the process.
Bonus Tip:
If your chosen veneer is light in color and your box is dark (as mine was), layer your veneer onto a thin sheet of white clay first. This barrier layer will prevent the dark base color from showing through the lighter design. It’s an extra step, but totally worth it for a crisp, clean look.
Conclusion
And there you have it, a sturdy, functional polymer clay box built from scraps and ready for decorating. Stay tuned for Part 2, where we’ll pretty it up with a cane veneer.
If you make your own, share it with me on Instagram @bysandracallander. I love seeing your creations!
