Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Tempered glass stars

Tempered glass stars

Tempered glass stars

I am working on an idea to deploy six pointed three dimensional glass stars on icy roads when needed to raise the coefficient of friction during stopping or turning/control events. I have produced a limited quantity and found excellent results that far exceed the usual sand/salt applications. The obvious problem is the broken glass itself when it fractures on the road surface. I understand that heat tempering such a small structure (about 1/4" point to point) is difficult. Is there a possible way to temper these glass stars so that they maintain their formed shape (not sharp) until they fracture and disintegrate to glass powder the way tempered glass does when it breaks.

The concept is explained more fully at icyroads.net

RE: Tempered glass stars

That looks interesting.
  • How do you know that glass is the best and cheapest material for this job?
  • I think that by time you put the heat and processing in to temper the stars, that glass may not be such a cheap alternative.
  • How do you plan on distributing the glass to the consumer?
  • It seems like sand or some type of off the shelf abrasive would be preferred so that the consumer would be able to replenish the system at any hardware store.
  • Can you deliver the abrasive onto the tire to aid traction during starting also?
  • The cynic in me says that there is not much proof that the icy surface the quicker stopping truck is on is the same. If you get more money for advertising a Zamboni cleaning the surfaces would add some credence.
  • Have you looked into regulations which would prohibit one from depositing materials onto the roadway?
  • Motorcyclists are not very fond of sand in the curves in early spring.

RE: Tempered glass stars

Well let's see:
Cheapest and best? I have been working on this problem (stopping on ice) for a very long time. Having tested most every type of abrasive I could find in all sorts of conditions I found that it comes down to the shape of the abrasive. It has to be able to bite into the ice in all conditions. Crushed rock (poultry grit) works fairly well at and around 32 degrees but if the ice is colder, say 5 or 10 degrees the grit can't overcome the hardness of the ice and acts more like a dull skate. Cost isn't so much the issue as what actually works.
At this point it is very clear that shape is all important. The glass stars or studs are very effective at all temperatures even at minus 30. What is not yet clear is the material.
Regulations? MnDOT has samples and has talked about a possible study but all this is very early.
Starting? Maybe but the device carries a rather small amount around 3 pounds so using as a convenience starting my not make sense.

Thanks for the input

RE: Tempered glass stars

Chem-tempering tends to leave you with a much smaller case-depth, resulting in lower internal stresses. These internal stresses are what cause the shattering youd describe above. You may find that chem-tempered stars don't disintegrate into fine powder like thermally tempered stars might.

"On the human scale, the laws of Newtonian Physics are non-negotiable"

RE: Tempered glass stars

Thanks for the reply.
Yes it looks like it will just take some old fashioned r&d to sort out.

RE: Tempered glass stars

None of the conventional tempering machines will be able to temper something 1/4" across, so you will need a custom machine or process. I suspect the process would be a conveyor belt made from metal mesh which rolls through an oven then on the outside has a continuous blast of cold air which cools the stars. One of the glass tempering machine makers like Glaston or NorthGlass could probably make a custom tempering machine. You might get a small scale prototype running for a few tens of thousands of dollars perhaps.

Chemical strengthening is a good idea. There is a shop in Philadelphia who I use a lot. It would be easy to try.

RE: Tempered glass stars

Thanks for the reply. This helps a lot.
The concept is so unusual and new that at this point we hope to just explore feasibility and look for contacts that can point us in a likely direction.
If all else starts to come together, possibly as early as this winter, there could be a budget for such a prototype.

RE: Tempered glass stars

Can you do a tetrahedron shape similar to a caltrop from medieval times combined with something like a Prince Rupert's drop? Might be able to cast the glass and then heat treat it... info entered into public domain...


RE: Tempered glass stars

The thing I would try would be to heat up a bunch of stars, yank them out of the oven, then blast them with cold air somehow. You could probably do some simple tests at an art glass blowing place with some compressed air. You need quite a bit of air to temper glass. They are set up to rent oven/studio time to artists, so would be relatively convenient.

Its possible you could try dropping the hot stars in oil or water too. Probably won't work, but would be easy to try!

RE: Tempered glass stars


I am interested in knowing the chemical strengthening shop you use in Philly. Can you share the name??


RE: Tempered glass stars

ceramicguy: i use a shop in Philly called Bent Glass Design for chemical strengthening. The owner is Steve Lerner. They are set up to serve both the transportation and architecture markets, and have a relatively large chem tank. They do a bit of work now with Gorilla glass too for electronics and automotive (and architecture if corning will let me!). I don't think they are set up for the optic lense market, though you could ask.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close