I never thought I’d say this but annealed vs. tempered glass seems simple enough. But when the glass panel arrives at the site and needs one more hole in it, it becomes very apparent that there is a difference. Annealed glass can be cut, drilled, shaped and even edge polished whereas tempered glass cannot be changed after it has gone through the heat treatment process. The reason for this is the internal stress that is put into the glass during the tempering process.
GLASVUE is an architectural glass manufacturer serving door, partition, façade, railing, and window projects. Its custom tempered glass can be supplied to final dimensions with edge processing, drilling, cutouts, surface treatment, and optional heat soak testing. A hole shifted by 3 mm or a forgotten hinge notch can turn a finished panel into scrap.
Can You Cut, Drill, or Polish Annealed vs Tempered Glass?
Finish all fabrication while the sheet is annealed, then temper it after drawing approval.
Cutting Differences
Annealed glass has relatively low internal stress. A fabricator can score straight pieces or use CNC equipment for approved shapes. Cutting a tempered panel can release stored stress across the sheet and cause sudden fragmentation.
Drilling Differences
Annealed glass can be drilled with suitable diamond tooling, coolant, steady support, and controlled feed speed. Hole location still matters because openings near an edge or corner may weaken the panel. Tempered glass should never receive new hinge holes, lock cutouts, countersinks, or cable ports after heat treatment.
Polishing Differences
Edge polishing removes material. Annealed glass can receive seamed, ground, flat-polished, pencil-polished, or beveled edges before tempering, subject to factory limits. Heavy grinding on tempered glass may reach the stressed zone, so even a small touch-up can cause later breakage.
| Fabrication Task | Annealed Glass | Finished Tempered Glass |
| Cut to Size | Usually possible | Breakage is likely |
| Drill Holes | Possible before tempering | Not safely possible |
| Add Notches | Possible before tempering | Not safely possible |
| Polish Edges | Normal factory step | Material removal is risky |
| Clean the Surface | Possible | Possible without structural grinding |
This annealed vs tempered glass comparison shows why a made-to-drawing panel is safer than altering a stock tempered sheet.
Why Does Tempered Glass Shatter When Modified?
Tempering improves strength and breakage behavior, but it prevents later structural fabrication.
Surface Compression
Glass is heated to roughly 650°C and cooled quickly with air. The outer surfaces cool first and form a strong compressive layer. This layer helps the panel resist ordinary impact, bending, and rapid temperature changes.
Internal Tension
The center of the piece of glass cools at a slower rate than the outer edges. This creates a tensile force in the glass which balances the compressive force on the outer surface. Tempered glass has 3-5 times the impact resistance and 4-5 times the bending strength of ordinary glass. When it does break, it produces small, blunt fragments instead of long, sharp splinters.
Edge-Damage Sensitivity
Chips and microcracks often start failure. Cutting, drilling, or deep grinding can cross the compressed layer and expose the tensile core. In an annealed vs tempered glass decision, annealed glass offers easier fabrication, while tempered glass provides higher strength after the final shape is fixed. The attached notes also require cutting, drilling, and edge work before tempering.
Which Processing Steps Must Come Before Tempering?
For any annealed vs tempered glass order, settle size, openings, and edge details before the furnace stage.
Final Size and Shape
Confirm length, width, thickness, corner shape, radius, and tolerance. The wall opening alone is not enough because frames, gaskets, hinges, and clearance take up space. A 4 mm error can stop a frameless door from fitting.
Holes, Notches, and Cutouts
Show every hole diameter, centre point, slot, notch, and internal corner. Add the hardware model because similar fittings often use different spacing. Rounded corners may be needed to reduce local stress.
Edgework and Surface Finish
State which edges remain visible and which sit inside a frame. The factory’s production capabilities cover cutting, edge processing, tempering, and heat soak treatment. Published capacity lists sheets up to 6,000 × 3,300 mm, thicknesses from 4 to 25 mm, and tempered surface stress of 120 MPa. Actual limits still depend on shape, holes, coatings, and glass build-up.
How Should You Order Custom Tempered Glass?
A useful quotation request lets the factory check the part before production.
Dimension and Tolerance Data
List final size, thickness, quantity, shape, tolerance, and exposed edges. Mark repeated panels G01, G02, and G03 so the factory and installer discuss the same piece.
Hardware and Cutout Drawings
Send a dimensioned PDF or DWG file. Mark hole diameters, centre lines, notch sizes, corner radii, orientation, and coating face. Separate left-hand and right-hand door panels. The project contact form accepts PDF and DWG drawings for technical review.
Thickness and Finish Selection
Choose thickness from panel size, support method, service load, local code, and hardware limits. Thicker glass is not always the best answer because added weight may exceed hinge ratings.
| Published Item | Figure |
| Tempering Temperature | About 650°C |
| Impact Resistance | 3–5 Times Ordinary Glass |
| Bending Strength | 4–5 Times Ordinary Glass |
| Listed Size | Up to 6,000 × 3,300 mm |
| Listed Thickness | 4–25 mm |
These are published product and factory figures, not universal limits for every processor.
What Should You Do When a Tempered Panel Does Not Fit?
A late annealed vs tempered glass change needs a careful check, not a grinder.
Tempered Glass Identification
Look for a permanent safety mark near a corner. Polarised lenses may also reveal stress patterns under suitable light. Do not identify the sheet by scoring, tapping, or drilling it.
Installation-System Adjustments
A qualified installer or engineer may be able to change a removable bead, gasket, setting block, channel, or hardware position. The revised assembly must still meet edge clearance, glass bite, drainage, load, and code requirements. Never force an oversized sheet into a frame.
Replacement Panel Specification
Replace the panel when its size, hole pattern, notch direction, edge finish, or coating face is wrong. Recheck the opening and hardware, revise the drawing, and mark each changed dimension. Keeping the faulty sheet nearby during review often helps trace the original error.
Get Custom Tempered Glass Made Right the First Time
Custom safety glass works best when design and fabrication stay in one process.
Project Drawing Review
Send final dimensions, hardware details, edge requirements, glass build-up, quantity, and application. Show how the panel connects to its frame and fittings.
Pre-Tempering Fabrication
The correct order is cutting, drilling, notching, edge processing, washing, heating, quenching, inspection, and packing. Optional heat soak testing can screen panels with certain internal inclusions before shipment, though it cannot remove every spontaneous-breakage risk.
Quote and Technical Support
For annealed vs tempered glass projects, approve every detail before heat treatment. Submit drawings through the technical enquiry page for review. A drawing-based quote lets the factory check size, hole pattern, edge finish, and installation purpose.
FAQ
Q: What Is the Main Annealed vs Tempered Glass Fabrication Difference?
A: Annealed glass can normally be cut, drilled, and polished. Tempered glass receives those operations before heat treatment and should not be structurally changed afterward.
Q: Can a Small Amount Be Ground off a Tempered Edge?
A: It is not a dependable repair. Grinding removes material from the stressed edge and may cause immediate or delayed breakage. A correctly sized replacement is safer.
Q: Can Scratches Be Polished out of Tempered Glass?
A: Very light marks may be treated by a specialist, but deep polishing can distort the view or weaken the surface. Request an inspection before abrasive work.