What is Pyrex?

Pyrex is simply a name brand of a particular glass formula properly known as Borosilicate Glass.  Borosilicate glass is a type of glass with the main glass-forming constituents being silica and boron oxide.  Boro(for short) has a very low COE (Coefficient of thermal Expansion)  which makes this glass formula unusually resistant to Thermal Shock.  Here at Eco-Straw.com we use Borosilicate Crystal for all of our drinking straws.  The formula of boro that we at Eco-Straw.com use is actually more resistant to thermal shock than Pyrex cookware because the COE is lower.  Pyrex has not been a true boro formula since 1980 when Pyrex incorporated “soda-lime” into their formula which raises the COE of the glass formula significantly.

What is thermal shock?

Simply put thermal shock in glass is what occurs when the temperature of the glass changes too drastically, which results in cracking and sometimes even minor explosions.  This could occur from heating too rapidly, or cooling too rapidly.  And the point at which thermal shock will occur varies drastically with each different glass formula.  In case you are wondering there are hundreds of commonly used glass formulas worldwide.

Putting COE’s into context:

So what various glass objects use what types of glass formulas?  I could write a novel on this very subject.  But I will keep it short and sweet.  Here are a few examples:

  • Our Glass Straws are a COE of 33coe.
  • Glass pipes people smoke out of are 33coe.
  • All laboratory grade glass vessels are 33coe.
  • Pyrex cookware is approximately 45coe(this is my guess, not a fact)
  • Margarita glasses from mexico are 96coe.
  • Most Art Glass Vases have a COE in the Neighborhood of 96-coe.
  • Most paperweights are 96 COE.
  • Most blown glass ornaments are 96coe.
  • Fused glass art is most commonly 90coe, but the past 5 years 96coe has also become common.
  • Most glass beads commonly referred to as Moretti, or Effetre, are 105coe.

Hopefully this article answers a few of your questions.  Thanks for shopping with Eco-Straw.com