Jodi McRaney RushoHappy Monday!  If you can smile about that, you’ll make it through anything.  Today I’m answering questions about mixing compatibilities in terms of bottles and frit, making polishing machines and using a ceramic kiln for glass.  These are actual reader questions and answers.  I’ve removed personal info for privacy reasons.  If you have a question, send it on over.


Q: can I use Uroboros 96 coe powdered frit on my bottles when I slump them or do I have to use the 82?? thank you. excited to slump some bottles 😀

A: Hello, thanks for your question. In my experience, 90 and 96 are not compatible with bottles. The Float Fire from Armstrong glass is a flexible coe powder that is 82 ± 2, which works very well with bottles and window glass.

If you do decide to experiment with the 96 on bottles, please let me know how it works out, I’m always interested to hear how the experiments go!

Q: We are trying to source a small grinding polishing machine to bevel and polish the top of a glass spirit or wine glass, although we cut the bottles using a diamond glass cutting disc in a wet tile cutter it still leaves an edge that needs beveling and polishing before they are truly safe to drink out of. Thanks for your time or in my language Diolch yn Fawr.

A: This is a very good question, I was in the same spot last spring, and what I ended up doing is locating a small bench top motor and threading the shaft to fit a convex diamond pad. I put the motor in a plastic bin with the shaft poking out through a hole to keep it away from water. This worked, but wasn’t terribly elegant so I ended up modifying a cheap tile saw with an adapter that allowed me to use diamond polishing pads, including a convex one that nicely polishes the inside rims. Here’s a post with photos about the tile saw hack:

If you decide to make something like this, the most critical piece is that little adapter. I would find that piece first! Here is a link to the convex diamond pads I use:

I still have original motor set up, I don’t have any photos, but if that would help, let me know and I’ll get some for you.

Q: First of all I love your web-site and all the helpful tips you provide. You are very inspirational. I do hope that you not mind me asking you a question. I am beginning to slump my first wine bottles in my kiln. I don’t mind saying that I am a bit nervous. I ran a test fire using an LT-3 sitter yesterday and eveything seemed to operate correctly. I have prepared my kiln and molds, and I would like to slump my first bottles this coming weekend and need your advise. I want to ensure I understand the firing schedule listed below and how to read it properly.

My plan is to slump two shelves of bottles (about six). Could you please advise which schedule would I use below? There is informaton overload on the internet and I just want to make sure I completely understand the firing process and how these components work.

A: I think I missed your weekend firing target, sorry about that! I get quite a few questions after a newsletter and this time was no exception. The awesome thing is they are all questions I haven’t had before, including yours!

Your question is very interesting because I have always been sure it would be possible to use a kiln with a sitter/cones for glass, but have never tried. The schedule that I use on my website is intended for kilns with a digital controller that can be programmed. However, that doesn’t mean we can’t figure out something with cones. Let’s talk about a couple of things real quick:

1. When firing multiple shelves (and I’ve done it for years, so I know you can), I have found it helps to elevate the bottom shelf so heat can get under it.

2. A slump firing schedule will make the bottles fall into themselves, but they will not be completely flat. If you’re going for completely flat, you should use a full fuse schedule.

now, cones:

it looks like cone 018 will get you to 1353, which is a great slump temperature. Does your kiln have any options for firing speed? Does your owners manual say approximately how fast each speed is? My kiln has a slow, medium and fast. The fast takes about 6-8 hours. I’d probably start with slow. The last thing we want is exploding bottles in the elements. Write down what time you start the firing and what time it ends, that will give us a good start point. Also, time how long it takes from the time the kiln shuts off to it being cool enough to open.

The last piece of the puzzle is the annealing temperature, which is 1060. You’d need to hold there for a while. Is there any way to a. tell what the temperature is inside the kiln, and b. manually or some other way hold at a particular temperature?

The cone chart I’m looking at shows cone 014 as 1540, which is a great full fuse temp for bottles.

How do you feel about trying it and letting me know how it goes? Photos would be awesome. If you want to send me the make and model of your particular kiln that would be awesome too. It looks like a Skutt, which is a great kiln, I have one and love it.

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