The Science of Strengthening Glass

Strengthen Glass

[Ben Krasnow] is at it again. This time he’s explaining a simple method for strengthening glass. As usual, he does a fantastic job of first demonstrating and explaining the problem and then following it up with a solution.

[Ben] first uses a simple rig to place a controlled amount of force against a glass microscope slide. His experiment shows that the slide shatters once about 30psi of force has been applied to the center of the slide.

[Ben] then goes on to explain that current methods for producing glass leave many tiny impurities, or cracks, in the glass. As the glass slide flexes, the inside edge is placed into a compression force while the outside edge is under tension. The glass is more easily able to handle the compression force. The tension is where things start to break down. The tension force eventually causes those tiny impurities to spread, resulting in the shattering glass.

One possible solution to this problem is to find a way to fill in those tiny impurities. According to [Ben], most glass has sodium added to it in order to lower the melting temperature. [Ben] explains that if you could replace some of these smaller sodium atoms with larger atoms, you could essentially “fill” many of the tiny impurities in the glass.

[Ben] does this himself by heating up a small vat of potassium nitrate. Once the powder becomes molten, he submerges the glass slides in the solution for several hours. During this time, some of the sodium atoms are replaced by potassium atoms due to the natural process of diffusion.

Once the slides have cooled down, [Ben] demonstrates that they become much stronger. When placed in the testing rig, the stronger slides do not break until the pressure gets between 60psi and 70psi. That’s twice as strong as the original glass. All that extra strength from such a simple process. Be sure to watch the full video below. [Read more...]

3D Printing Directly Onto Your iPad Screen

ipad 3d printing bed

Corning’s Gorilla Glass is very scratch resistant, shatter resistant, heat resistant, and even flexible material — it’s actually a perfect candidate to be used as a print bed material. The only problem is it’s not typically sold outside of consumer products, but that’s when [cvbrg] realized an iPad’s replacement screen would fit his maker-bot perfectly.

One of the biggest problems people encounter with 3D printing usually involves the print bed. Sometimes the prints don’t stick, the edges peel, or it even gets stuck on there too well when it’s done! A popular solution is a borosilicate glass bed, which typically helps with adhesion and surface finish — but again, sometimes the prints don’t want to come off! Sometimes parts can even tear up pieces of the glass bed when you’re trying to remove them. People usually counteract this with Kapton tape, which can become a headache in its own right — trying to apply it bubble free, tearing it, doing it all over again…

Using an iPad’s screen (only about $15 on eBay), means you can hack and jab at the print bed all you want without fear of breaking it – It even has a bit of flex to it to help pry your parts off. Did we mention it also has a very uniform flatness, good thermal conductivity, and resistant to pretty much all solvents?

[Read more...]

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