This is an easy way to make a wood mold for blowing round glasses or vases or anything like that. The construction of this mold is inspired by a Czech or Russian (that's my guess) style mold that I came across while living in Denmark. This Instructable won't go too deep into the skill it takes to blow the pieces, but if you want to blow the pieces yourself, you might be able to find a glass studio in your area that offers classes. With practice, you can do it yourself. If not, a local glassblower will be able to make pieces from your mold, for a decent price.
Most traditional wooden molds are made from a solid piece of wood. The interior shape is hollowed out on a wood lathe, which requires a tremendous amount of skill and a special cutting jig that is mounted on the lathe. After the inside shape is removed, the wood is then split (if the shape has undercuts) and air holes are drilled through the walls.
For production glassblowing, the molds are usually made from graphite or metal. The advantage is that they will last a very very long time. The wood mold shown here is much much cheaper and easier to make, and you can still produce dozens upon dozens of pieces before it wears out. Plaster can also be used to make molds, but I find this very tedious and messy and prefer making these wooden molds instead.
I wanted to make more of the drinking glasses that I'd designed a few years ago. I was down to one glass, blown by my mentor, the late Charlie Meaker, and became a bit concerned about breaking it. So I decided to make some backups that I could use everyday without worry.
The shape of my glass is pretty basic, just a low and wide drinking glass with a chamfered base. It doesn't have undercuts, so the mold-making is simple, and the glass can pull straight out the top after it's blown. Any shape with undercuts will require a split mold, which complicates things a little bit. A split mold will usually need an assistant to hold it shut, or some kind of catch to keep it together.
When designing a glass, it's most important to think about what you want to drink. In this case, I made a glass for all around use, from water, juice, beer, to wine or whiskey. It's blown fairly thin at the rim, but thicker at the base so it's still durable and has a good weight to it.
It's just as important to think about ergonomics. A glass that is too wide or too tall can be awkward to hold. Picking it up a glass should be easy, comfortable, and natural. A glass with a thick rim isn't very pleasant to drink from, and a very thin rim can feel too delicate for anything other than wine.
Glasses come in all shapes and sizes. Whiskey glasses are usually heavy, wide, and low. For juice, I like a tall and narrow glass. Shot glasses are always small and durable, and beer glasses can be so big they need handles. Wine glasses have a whole science attached to them, just look at the selection offered by a company like Riedel. For hot drinks, like coffee and tea, I prefer something ceramic. They usually have a handle, because the heat transfers to the walls and it can be too hot to hold.
This mold-making technique can also be used to create larger glass pieces, like vases. Think about what kind of flowers will be displayed. How long are the stems? How much water should it hold? It should be heavy at the base so it doesn't tip over easily.
Do some research, sketch out some shapes, and decide on a direction to take. It's fairly easy to create a few different shapes in a 3d modeling program, using the Revolve command. When you know what you want to make, create a 1:1 template.
The next step to making the mold is to draw out a full scale 2-dimensional template. I do this by laying out the shape on paper, connecting the dots, and then cutting it out with scissors. Use thicker card stock or 1/4" thick wood if you want to preserve the template.