Bent Glass Technique


I’ve been working on a lamp design, and this is a bent piece of glass I’ve been looking to get made.
My search has already taken me across the nation (via email), to people specializing in glassblowing, stained glass, cast/molded glass, bent glass, and more. No one has been able to take on this task, and I’m beginning to think it’ll be too difficult to pull off using glass.

Sure, the easy answer would be to just bend a plastic sheet, but glass has such a fantastic feeling, is more environmentally sound, and will add a much greater value to the piece.

Any suggestions of how to pull this off would be fantastic,
Thanks in advance!

Glass is a tough animal, especially when you start forming it.

What are the overall dimensions of the piece?

Thanks for the quick response!
It’s in the 6x6x12" range, but I’m completely open to modifying the design so it can actually be made real.

This should help, some dimensioning:

I imagine it might take some experimentation, and lots of broken glass… and in that case, would I just end up with a super delicate lamp?

Perhaps safety or pyrex glass would be excellent, though no doubt expensive and probably impossible to bend.

Very tricky, but bent glass tables exist. The glass has to be heated to softening temperature and supported on a perfectly smooth surface to not mark the glass, and it will slowly move with gravity to the final shape. Then it has to be cooled very slowly, a week or more probably, as to not be under tension when cooled. A tight radius like you have rendered, I have not seen before.

Here is a PDF of some information on thicknesses and radius. Precision Glass Bending : Custom Bent Glass Specialists

Thanks for the info, I actually contacted e-bent glass and they declined because they couldn’t achieve this tight of a radius, and sent me on to two other places, Fox Fire Glass, and Dlubak, both of which couldn’t help me either. Hmm.

I’m planning on frosting the inside surface to diffuse light, so that’s one concern gone!

You may want to look into slumping glass. Basically it’s heat bent over a form. You will probably have to increase that inside radius significantly. Is this intended to be structural in some way? Or just decorative? That may change how everything is done, too.

Slumping glass sounds like the right approach.

It doesn’t need to be very structural; it will be held together with wood, sitting in channels so the glass won’t be a contact point to whatever surface it’s on. It’s a simple, geometric, block-shaped lamp… I just think a single piece of glass would be elegant and different than a bent plastic, ya know?

Just a thought… I could alternatively just butt-up panes of glass with a clear silicone-esque glue similar to aquarium construction, right? So long as the seam doesn’t produce obvious shadows, I’d be down with that.
Might be more structurally sound, yeah?

check out:

I was thinking slumped glass as a possibility too. However, I can’t recall seeing any architectural slumped glass pieces that have tight corner bends, anyone know of any examples?

How about something like this? Maybe not the aesthetic you were looking for. Much easier to manufacture, although the fasteners might have to be different or at least rubber insulated.

Ha! That’s funny!

You ever bored a hole through the end of a sheet of glass like that? Funny…

I emailed them and they never responded to me. It does seem like that tight corner is difficult to slump over… Haven’t found many good examples.

Interesting idea, but I think NURB is right. Also, I’d prefer not using excess hardware, or anything that would too obviously obstruct light from shining out.

I think using three separate sheets and butt jointing them (like the previous post of an Aquarium, or the seams of a glass shower) might be the best solution to use glass.

…is it possible to miter joint glass? haha.

Check out the Angle Bend:

This looks more like they’re selling the equipment though… and they’re based out of Hong Kong.
Kinda want to keep it stateside. Thoughts?

The fish tank approach probably won’t work unless I’m missing more of the design. The fish tank gets it’s structure from the plastic that holds everything in place, the silicone is just sealing it. You will definitely notice the shadows of the lamp if you try to use 3 pieces of glass. If your design needs the pure planes, you may be better off just leaving the openings and fixing the glass in place using whatever holds that part of the lamp.

Based on the size I see no way of achieving that at that size, the glass vendors would be able to give you a realistic radius you’d be able to achieve in production.

Sadly industrial design purity is generally tempered by the ability to experiment with materials. You either need to have a vendor that can do it, or be Apple and have enough push to endure the massive material studies needed to push the limits of it.

Thanks a ton, Cyberdemon. Well put.

Thermal expansion and contraction is the biggest thing to factor in to glass work. Slumping can be done very quickly and molten which does not allow any verticals because the glass just runs down to a pool. Slumping can also be done very slowly. The biggest problem I see is that with slumping is that the shaping form in the middle will prevent the contraction of the glass and it will crack in the middle as the “legs” hold the middle in tension.

The approach might be to heat the whole glass sheet up to 1100 degrees, which I recall is the magic stress free temperature, (or maybe 900) then use something like a ribbon heating arrangement to locally heat the bending zones like a line bender. Then manually bend the sheet quickly, asbestos gloves, fixtures, and get it fast back into the annealing oven for stress relieved slow cooling.

There are plenty of ways to build hot glass kilns, not really that difficult, and experiment.

All this being said, you could buy a sheet of slight green tinted Plexiglas, embed a nichrome wire in a slot, heat a line in the Plexiglas, bend it, and you are done. Line bending. I think due to the high energy costs of forming glass that the eco-ness of acrylic could be argued. As well as shatter-proof safety. Can be done on your desktop.

Last thing to consider is UV gluing sheets of glass together. This is common in furniture and glass art. Miters are possible. Drilling holes is possible. Managing thermal expansion and contraction of different materials in contact with the glass is a must, which is why silicone rubber is so commonly used.

Give these guys a call…

under accessories, check out the two “optically bonded” pieces. Might be a direction to check out.

my friend glass worskhop recently made a rostrum entirely from glass, they used UV glue which is more expensive than silicone glue but looks nicer. Its pretty sturdy as well.

Invisible UV adhesive is the right stuff to fabricate a butt-jointed glass enclosure.

Edit: I see now that others covered this.

If you want slumped glass the tool/mold will likely cost tens of thousands of dollars. Rayotek Scientific in San Diego is the best US option I know of for slumped glass. They do work for the DOD and NASA. I dealt with them to get a project quoted, they were very helpful. Rayotek is one of the companies included in “Manufacturing Processes For Design Professional” by Rob Thompson which is book that I highly recommend.

Wow, thanks for the info! I’ve never heard of UV gluing, definitely looks worth checking out.
That, or as you said, just bend Plexi.

Nice find, I’ll give them a ring.

Cool, another vote for UV glue, thanks.

Great insight, tens of thousands is definitely out of the budget for this project. UV glue seems worth pursuing. I’ll check out that book; I’ve been looking to expand my knowledge of manufacturing for sure.

Thanks everyone so far for your help and suggestions on this.

Could it be a thick, clear plastic sheet/plate - maybe 1in thick?

Seems costly, but doing it in glass doesn’t seem that cheap either. It could be much easier to work with and still have the same effect…

Another option would be to work with the bend radius that the glass companies are giving you. Nothing sparks creativity like a constraint

PS I’ve hear ‘draped glass’ thrown around once or twice, might be the Euro term for ‘slumped glass’