Glass battle: "Milk Glass" vs Milk Glass

Milk glass.
Your mind meanders vintage Pyrex and the cousins – Fire King, Glasbake, Federal Glass and Hazel Atlas, ending in a collection of quaint mugs of white, adorned in patterns and sass.

These are NOT milk glass.

That’s right, the retro cousins of today’s kitchenware are not true milk glass. Instead they are white configurations of soda-lime glass, often jauntily adorned in the color palette of the era (40-80s for Pyrex).

White glass, not milk glass.

Say what?
White glass?
But but… the Ebay & Etsy machines assure that Pyrex, the cousins and the quaint mugs ARE milk glass! Lies and deception!

Before you go ape on those dealing in retro antiquities, note that it is easy to confuse white glass and milk glass at times. Additionally “milk glass” has become interchangeable with glass that is white, much like buffalo check is swapped for buffalo plaid (its actually buffalo check…).

I digress.

The difference of “milk glass” and authentic milk glass apart is much more notable in person. Start with the color of the glass.

Real live milk glass is whiter, like a crisp glass of freshly poured milk. During creation, opacifiers are added to the glass mixture to give a greater opaqueness (aka less see through), the additives often bone ash or tin dioxide.

Milk glass can be other colors aside from white! Blue, pink, yellow, brown or black are colors you may traipse across in your milk glass adventuring.

If it looks like someone poured a bit of strawberries or blueberries into a glass of milk and swirled the mixture to an even consistency, its a non white milk glass.

And each authentic piece of milk glass is a carrier of the Tyndall effect.

The Tyndall effect?

Tyndall Effect
noun Physical Chemistry
the visible path of light produced by the scattering action (Tyndall effect) of the particles in a colloidal solution on a beam of light passed through it.

Uh…… what?

Basically, due to adding those handy dandy opacifiers to the glass mixture, it becomes colloidal, or a solution with particles in it. The particles not only give the glass its coloration but also scatter light that passes through them.

Blue light is scattered more strongly than red light in the Tyndall effect.

Which means true milk glass carries a blueish tone, while light that shines through it appears a reddish to orangish color. Often most visible on edges as “rim of fire” if you will.

Another distinguishing factor between milk glass & white is opacity.

Milk glass has the opacity of a bucket of new white paint, and holds no translucency – except when the glass mold wasn’t filled in entirely leaving little blips of blueish hazy glass heavy in the Tyndall effect.

White glass has a slight translucency in its skin, a warmth and look that is a bit softer in comparison to its cousin milk glass and distant cousin ceramic.

Can you tell the difference in the pair below?

And…
For more rip roaring confusion, let’s add more glass: opal glass & opalescent glass.

Opal glass IS milk glass! Often authentic milk glass is referenced as opal glass, though opal glass may hold more of a translucent appearance, the coloration reminiscent of watered down milk. (The Google beast is a bit vague at describing opal glass, favoring milk glass & opalescent glass.)

Opalescent glass IS NOT milk glass but is a very close sibling, related by the opacifiers used in creation (either aluminum oxide or bone ash). Opalescent glass is a carrier of the Tyndall effect. It is translucent with a slight hazy or milky look.