Convex Glass FAQ

We carry convex glass also known as bubble glass or domed glass in many antique sizes and shapes along with their modern equivalents such as: Oval frames, round frames, rectangle frames, and other non-traditional shaped frames. Although convex glass will fit all the picture frames we sell they are most commonly ordered with our Vintage Collection. 

What is the difference between convex glass and bubble glass?

They are simply different names for the same product. 

Is there a difference between concave and convex glass?

There is no difference. The glass is concave or convex depending on the perspective. 

How is convex glass measured?

Like flat glass, convex bubble glass is measured length and width directly across the glass (not around the bend of the glass). Most of our convex glass has a depth of 3/4" to 1", but deeper bends are possible.

Where can I find unusual antique sizes of convex glass for antique picture frames?

Many of our most popular convex glass sizes are antique sizes like the Oval Picture Frame Size 13 1/2" x 19 5/8". Many people think these odd antique sizes are no longer available, but at InLine Ovals most of these antique picture frames and convex glass are standard sizes.

We currently stock over 50 standard sizes of convex glass and we also custom bend any size of convex bubble glass to fit oval picture frames up to 22" x 28" and circle picture frames up to 24". A paper tracing of the custom bend is required.  The glass will be cut to the line drawn on the paper template. To produce your custom size convex glass allow 3-4 weeks delivery after we receive the tracing.  See the videos below for tips and instructions for working with convex glass. 

How do I measure my convex glass?

How is convex glass installed?

How do I find convex glass to fit an antique frame?

How do I Order Custom Sized Convex Glass?

What is convex glass used for?

Most bubble glass or convex glass is used to cover old antique portraits in which the photographs were convex. We sell convex glass replacements to fit actual antique frames, to replace broken pieces in clocks, gauges and other instruments, as well as to fit our own antique replica frames. 

How is convex glass bent?

Flat glass is laid into frame molds.  The glass is then heated to temperatures that allow the glass to slump. Longer heat creates a deeper bend thus creating what is know as bubble glass or convex glass.  

It is also possible to have your modern prints made into a convex portrait Just as the antique replica oval frames, round frames and convex glass are available today, For information on having convex pictures created please visit the Georgian Bay Art Conservation.

What is the history behind convex glass?

Over half of the picture frames produced in America by some of the largest picture frame factories in the late 1800's up to about 1940 were oval, round, or antique octagon.  Today less than 5% of all picture frames produced are oval frames.  A large number of these old frames were family portraits that were then covered with convex glass. Many attics and basements are home to these family heirlooms framed in antique frames and often broken convex bubble glass.  We are able to bend convex glass, thus providing replacements for these images. 

Should I choose an acrylic dome or deep convex glass?

Convex glass normally has a bend of about 3/4" to 1”. Items that have a depth more than a photo or canvas, you may consider  our acrylic domes which fit all our frames and range in depth from 2.5" up to 7".