Topic: Machine made glassware — Safety Rim: any input?

[David E]

Can anyone enlighten me on the tiny bump found on the rim of Dema machine-made glassware?

Following communication with Christine, she tells me this was called a 'Safety Rim' to reduce the likelihood of chipping. I have found mention here under the name 'SIRA':

http://www.rkl-glas.de/_products/catering.php

Other companies also mention 'safety rims', but is this bump a consequence of machine-made glass, or an intentional inclusion for this purpose?

I also found mention that safety rims do not feature before 1970 - can anyone confirm this?

[Pinkspoons]

On glass-forums.com Connie mentioned that the safety rim was patented by Libbeys pre-1930.

I have a Holmegaard cannister, mould-blown, dating from 1930 which also features one - so it's not just machine-made glass.

[David E]

Thanks Nic: that rules out the date then. Just need to know whether the 'bump' is a side-effect, or deliberate. I think Stephen might be able to help here.

[Connie]

What bump are you talking about?  Most safety rim glasses will have a small bump where the glass roll meets.  I think it is a artifact of manufacture.

[Pinkspoons]

As far as I know, the bump is what makes the safety rim safe.  

A thicker, rounded rim atop an otherwise thin and fragile piece of glass adds stability to the form, as opposed to just polishing it. The thickness adds strength and the rounded nature of it deflects impacts to some extent. But this is just my own speculation.

[David E]

Connie, it would appear you have answered my question - the bump is a side-effect of manufacture - but Nic's suggestion of a thicker rim might appear to have credence.

More specifically, this is in relation to the glassware supplied by Chance: the bump I can feel on Dema glasses is barely detectable, but isn't apparent at all on earlier items from Nazeing Glassworks.

[Ivo]

Polishing is a secondary operation while the safety rim is made in one single machine operation & therefore cheaper. Polished rims are infinitely more elegant. Better to have glass with a thicker rim if you're going to knock it around, as you do in restaurants. 

In a 4 star restaurant you'll serve the wine from Riedels - with a polished rim. If you have a Pizzeria, you use Bormioli or Dema with a safety rim.

 

[David E]

... but isn't apparent at all on earlier items from Nazeing Glassworks

Add: ... which were blown items, of course

[Connie]

David -

I think I was confused by your use of the term "bump".  If by bump you mean that roll or bead of glass that is continuous around the top rim - then that IS the safety rim. But on some safety rim glasses you can see a thickening or lump at just 1 small area on the rim which is where the 2 ends of the roll of glass meet - that is an artifact of manufacture.

[Lustrousstone]

Which still leaves the question as to whether the Dema glasses had a deliberate safety rim or were just poorly made