Polishing Borosilicate Glass: Borosilicate Glass (CTE 3.3 x 10^-6 /K, 360 nm – 2.0 um); Polishing to flatness to lambda/4 per 25 mm. Single-piece prototypes to production volumes, quoted from your drawing.
Ask any process engineer what makes borosilicate glass difficult and the answer is specific: sheet stock carries more thickness variation than float wafer stock, so lapping is often the first step. Our polishing line is tooled around exactly that – pitch and polyurethane pad polishers with cerium oxide slurry – holding flatness to lambda/4 per 25 mm on parts from 0.2 – 50 mm thick.
Specification envelope
| Material | Borosilicate Glass (3.3 expansion group per ISO 3585) |
|---|---|
| Thermal expansion (CTE) | 3.3 x 10^-6 /K |
| Service temperature | 450 C continuous |
| Transmission range | 360 nm – 2.0 um |
| Density | 2.23 g/cm3 |
| Knoop hardness | 480 kg/mm2 |
| Refractive index | 1.473 @ 587 nm |
| Stock thickness | 0.50 – 30 mm |
| Maximum blank size | 600 x 400 mm |
| Process | Polishing |
| Working tolerance | flatness to lambda/4 per 25 mm |
| Minimum feature | Ra below 1 nm |
| Surface finish | scratch-dig 40/20 to 20/10 |
| Thickness window | 0.2 – 50 mm |
| Edge condition | polished bevels available |
| RFQ inputs | PDF/DXF/STEP drawing, quantity brackets, surface and edge spec |
Capabilities and limits
The core strength of Polishing is optical-grade faces with certified scratch-dig and interferometer-verified flatness. The honest limit: steep aspect parts and deep pockets polish unevenly; those faces are specified as fine-ground. Both belong on the drawing before quoting, not after.
One material, many routes: on Borosilicate Glass we also quote coring, lapping, dicing, double-side polishing, and multi-step drawings are the norm rather than the exception.
Design guidance
Before sending the RFQ, check these against your drawing:
- Material note: sheet stock carries more thickness variation than float wafer stock, so lapping is often the first step.
- Process boundary: steep aspect parts and deep pockets polish unevenly; those faces are specified as fine-ground.
- Over-specification is the quiet budget killer: a 20/10 scratch-dig face costs roughly three times an 80/50 face, so grade each surface individually.
The full rules live in our tolerance design guide and holes and edges design guide.
Application context
The recurring buyers of polishing borosilicate glass: medical diagnostics (flow cells, slides, microplate bottoms, cuvette windows); scientific instruments (reference flats, cells, prism mounts, stage inserts); laboratory instruments (cuvettes, sight glasses, stir-cell windows). Background reading on the underlying material science: ISO 3585 borosilicate glass 3.3.
Dimensions still moving? Configure this part live in the 3D builder below, or open the full custom glass machining 3D builder to start from a blank canvas.
Useful companion pages: glass sandblasting, material selection guide, optical polishing capability.
Common questions
What tolerances are achievable on Borosilicate Glass parts?
Ground features hold +/-0.01 mm and lapped thickness reaches +/-0.003 mm. Sheet stock carries more thickness variation than float wafer stock, so lapping is often the first step.
What thickness range do you stock for Borosilicate Glass?
Standard stock spans 0.50 – 30 mm, with blanks up to 600 x 400 mm. Other formats are sourced per order.
How does Borosilicate Glass behave under heat?
CTE is 3.3 x 10^-6 /K and continuous service reaches 450 C continuous, which is what drives its use where chemical durability matters.
What accuracy does polishing hold?
Flatness to lambda/4 per 25 mm with minimum features of Ra below 1 nm. Steep aspect parts and deep pockets polish unevenly; those faces are specified as fine-ground.
What equipment runs the polishing work?
Pitch and polyurethane pad polishers with cerium oxide slurry.
Specifications on this page were last reviewed by our engineering team in July 2026.