BOROFLOAT®

Borofloat is a borosilicate float glass made by SCHOTT, which introduced it in 1993 as the first floated borosilicate glass. Its low thermal expansion lets it take heat and temperature change better than ordinary soda-lime glass.

Two glass families sit on the Borofloat page at BoilerSupplies.com. Quality Borosilicate Flat Glass Circles are cut discs for sight and observation windows. The Borosilicate Glass, Cobalt Blue, Fused Quartz Glass family covers three materials, picked by the job. Clear borosilicate takes heat and temperature swings. Cobalt blue lets an operator look at a flame without the glare. Fused quartz goes where the heat runs higher than borosilicate is meant for. The circles sit beside the sight glass, gasket and gauge glass lines on the same pages.

Key facts

• Borofloat is a borosilicate float glass made by SCHOTT.

• SCHOTT introduced Borofloat in 1993 as the first floated borosilicate glass.

• Borosilicate glass has low thermal expansion, so it tolerates heat and temperature change better than soda-lime glass.

• Cobalt blue glass cuts the glare when an operator looks at a flame.

• Fused quartz is used where the heat is higher than borosilicate is meant for.

• In-stock small-pack orders placed before 2:00 PM EST, Monday through Friday, ship the same day.

What is Borofloat glass?

Borofloat is a borosilicate float glass made by SCHOTT, introduced in 1993 as the first floated borosilicate glass. Its low thermal expansion lets it take heat and fast temperature change better than soda-lime glass. On BoilerSupplies.com, the Borofloat page lists two families: Quality Borosilicate Flat Glass Circles, and Borosilicate Glass, Cobalt Blue, Fused Quartz Glass.

What is a sight circle, glass disc or observation window called on BoilerSupplies.com?

Quality Borosilicate Flat Glass Circles. Sight circle, glass disc and observation window are trade names for a flat, round disc of glass cut to fit an opening so an operator can see inside. The diameter, the thickness and what the window looks into matter more than the name.

When does a sight window need cobalt blue or fused quartz instead of clear borosilicate?

Cobalt blue goes where an operator watches a flame and needs the glare cut. Fused quartz goes where the heat runs higher than borosilicate is meant for. Clear borosilicate covers the other sight and observation windows that see heat and temperature change. Describe the service in the quote request if in doubt.

How is a replacement borosilicate circle sized?

A replacement borosilicate circle is sized from the old disc. Measure its diameter and thickness, or take them off the drawing for the fitting, and note whether it is clear, cobalt blue or quartz. Add what the window looks into and the quantity, and send those details with the quote request.

Why use borosilicate instead of plain window glass in a sight port?

Plain soda-lime glass expands more with heat, so a hot port meeting a cold draft can crack it. Borosilicate glass has low thermal expansion and tolerates heat and fast temperature change better. Borofloat is a borosilicate glass of that kind, and fused quartz takes over where the heat runs higher.

Send the old disc's diameter and thickness, the glass type and the quantity through BoilerSupplies.com for a quote on borosilicate circles, or phone them in to 1-770-957-9599, toll free 1-800-780-3776.