HOW I DESIGNED THE PERFECT WOODEN MOULD

I’ve been working on a wooden mould recently, and honestly, it’s like trying to create a spa treatment for molten glass. Keep the wood fresh, give it air to breathe and design it well, and everything behaves beautifully. Ignore any of that and the mould starts smoking like it’s auditioning for a fire safety poster.

Photo by Orfeo Marques Mandin

Here’s what I learned while designing mine.

Choosing the Wood

Fruit trees are the sweet spot. Cherry, apple, pear, all of them have that lovely dense, even grain that holds up against heat and gives a smooth finish on the glass. Cherry is the top choice because it lasts longer and steams in a nice, predictable way.

I went with fresh ash for this mould. Not quite cherry, but honestly, still brilliant. The one rule I live by: the fresher the wood, the better. Once wood dries out too much, it scorches quickly and stops giving that gentle controlled steam you actually rely on during blowing. No one wants their mould behaving like a dry log in a campfire.

Building in Air Channels

When hot glass meets damp wood, the moisture flashes into steam instantly. If that steam can’t escape, you get all sorts of chaos. Think spitting, hissing and the occasional personal insult from your equipment.

So I always include air channels in the design. They’re not decorative. They let steam out and stop the mould from overcooking itself. The result is smoother turning, cleaner shaping and a mould that actually survives longer than an afternoon.

Why I Like a Generous Opening

I learned early on that if your mould’s opening is stingy, everything becomes a battle. The pipe, the moyle, the slightly wonky gather you pretend was intentional, they all need space to enter cleanly.

Too tight and you give yourself a lot more work in trying to fit your glass in the hole. In my PDF drawing you can see the wide opening and how it allows proper clearance around the pipe and gather. It makes all the difference when lowering the glass into the mould with confidence. Negative Mold Rendering with Me…

Why I Designed a Three-Part Mould

This mould is in three parts, and honestly, I’d never go back. The two hinged sides open outwards, which means I can lower the hot glass straight onto the smooth bottom section without worrying about trapping it between two tight walls.

More control, less stress, and a much nicer shaping process. The glass lands where I want it, not where the mould forces it. The perspective and side views in the PDF make this really clear. Negative Mold Rendering with Me…

Why 3D Drawings Matter

If you’re giving your mould design to a carpenter, a drawing is good, but a 3D rendering is basically a love letter to clarity. My PDF shows the measurements, hinge placement, cross sections and the shape of the cavity, which meant the carpenter could build exactly what I imagined.

And if you ever have your pieces blown elsewhere, the glassblower benefits too. A great mould is wonderful, but a visual representation of what you want is even better. It removes guesswork and lets them understand your intention instantly.

Why My Wooden Mould Now Lives in a Bucket of Murky Water

One thing I didn’t realise at the start is that once the mould is finished, it more or less moves into its new home permanently. It has to live submerged in water so it never dries out or cracks. Even when I am not using it, it just sits there soaking like a very committed spa guest. The water gets murky over time, but that actually works in my favour. It behaves a bit like a natural slip, helping the glass glide more cleanly inside the mould. So now I apparently have a new pet. It just lives in a bucket, drinks a lot and asks for very little.

Designing this mould taught me that good glass starts long before you gather anything from the furnace. It begins with the wood, the drawing, the planning and the care you put in beforehand. If the mould is thoughtful, the blowing becomes effortless. And honestly, there’s nothing better than seeing your idea go from screen to timber to glowing form in your hands.