Today I’m answering reader email questions.  The personal details have been removed for privacy.  If you have a burning (ha!) glass question, please send it on over using the contact form.  Please be patient, I receive hundreds of emails a day, sometimes I get a little behind schedule.


First, a huge Thank You to everyone who sent Thanksgiving messages, it was inspiring to hear from so many people from so many places, I love the glass community!  Now, I have a fresh cup of coffee, so here we go!

Q:  can stoneware milds be used for glass casting? There are some cute Brown Bag cookie molds that I think would make sweet ornaments and suncatchers.  There are stoneware.  can they be used for glass casting?  Stoneware means they have been fired at a higher temperature than bisque (used to do pottery…still want to).

A:  Sorry for the delay in email answering, I’m woefully behind right now.  I would think the stoneware cookie molds would work perfectly.  No guarantee, of course, but I’ve used some stoneware paper casting molds, and one cookie mold, and had no trouble at all.  Make sure they are kiln washed. I’d love to see them when you’re finished.

Q:  Hi Jodi,

I want to tell you how you inspired me and made me try to do art from recycled glass. I follow you constantly and you always have interesting and original ideas. I trued some glass fusing, slumping and it goes good but i’m interested in making glass sculptures about 20x20x30 cm big from recycled glass bottles, but i’m new to the glass world and i have some issues.  I’ve watch a lot of videos about glass casting and they always use plaster for glass casting but it cracks when fired and the glass flows out of the mold. If you can tell me which is the best material for making molds for glass casting. If you can point me to some literature for how to make glass casting i will be very thankful. Can you tell me the best schedule for glass casting. I’ve found some schedules but they are all for small pieces and the glass comes out just barely fused or cracked. Thank you in advance,

A: Two things, well, three.   I think the best mix for plaster casting is pottery plaster #1 mixed with silica 325 mesh.  The silica mixed in makes the plaster much more tolerant to heat.  The pottery plaster is a finer grade than plaster of paris, so it holds details better, as well as survives the heat.

I also wrap my plaster casts with stainless wire to hold them together during firing.

For firing schedules, they can be so variable for sculpture depending on thickness overall, and varying thickness.  It would probably be good for you to locate a copy of Graham Stone’s book ‘Glass Firing Schedules’

This book has firing schedules for many, many thicknesses of glass and types of glass as well as sculpture casting tips.

The last thing is, do remember that not all bottle glass is going to be compatible, so I would strongly suggest testing the different bottles with each other in a fuse before putting them all in a sculpture together.  If you are mixing bottles now, some of the cracking you are seeing may be compatibility related.


Q:  If i have a bottle bottom cut very close to the bottom and no punt do you put the cut side up or down??

A:  I usually put it cut side up, for no particular reason, now that I’m thinking about it.