Can a hole be drilled in tempered glass after it's installed?

No. Tempered glass is under permanent internal stress, and any cutting, drilling or edge modification after tempering can cause the pane to break. All holes, notches, cut-outs and edge shaping have to be finished before the glass goes into the tempering furnace, which is why measurements and hardware positions need to be confirmed before fabrication begins.

What's the difference between a seamed edge and a polished edge?

A seamed or arrised edge has its sharp corner knocked off for safe handling but stays visibly ground and matte; it is a safety treatment meant to be concealed behind a frame, channel or trim. A polished edge is ground smooth and buffed clear, and it is meant to be seen — it is the standard choice for frameless work where the edge is exposed.

Does edge finish affect breakage risk?

Edge damage — nicks, chips and micro-fractures introduced during handling or a poor cut — is one of the more common origin points for glass failure, tempered or not. A clean, correctly finished edge with no surface damage handles stress far better than a rough or nicked one. This is separate from the nickel sulfide phenomenon discussed in our tempered glass guide, which originates inside the glass rather than at the edge.

Can curved or radius glass get any edge finish?

Most standard finishes — ground, flat-polished, pencil-polished — can be applied to curved and radius-cut edges, though curved work generally takes more time on the edging machine than a straight cut. Mitred edges are the exception, since a true mitre depends on two flat edges meeting at a controlled angle.

Fabrication Explainer

Glass edge finishes and the order fabrication has to happen in

Edgework looks like a finishing touch, but it is one of the earliest and least reversible decisions in a glass project. This guide covers the common edge finishes, why they exist, and the fabrication sequence — cutting, drilling and shaping before tempering — that governs almost everything else about how a piece of glass can be modified later.

Written by the Gloria Glass installation team

1. Why edges matter beyond appearance

A cut edge of glass is its weakest surface. Fresh cuts carry microscopic flaws that concentrate stress, and any additional damage — a chip from a dropped tool, a nick from careless handling — adds to that concentration. Edge finishing removes the roughest of those flaws and, on exposed edges, does it in a way that also looks intentional. Both purposes matter: a poorly finished edge is both unattractive and more likely to be the point where a pane eventually fails under stress it would otherwise have handled.

2. Common edge types

Edge type	Typical use
As-cut / raw	Never left exposed on finished work; sharp and unsafe to handle
Arrised / seamed	Sharp corner removed for safe handling; concealed edges, behind frames or trim
Ground / flat-ground	Smooth matte flat edge; a step up from seamed, still usually concealed
Flat-polished	Clear, glossy flat edge; standard for exposed frameless work — partitions, shelves, railings
Pencil-polished	Rounded, bullnose-style polished edge; shelving, table tops, mirrors without a frame
Mitred	Angled edge cut to join two panes at a corner with no visible frame
Bevelled	Angled decorative band around the perimeter; mirrors, tabletops, decorative panels

None of these is objectively "better" — they suit different applications. A partition panel and a decorative mirror have entirely different edge briefs, and the choice is usually settled by whether the edge will be seen, touched, or hidden.

3. Edge quality, damage and breakage risk

A correctly finished edge has no chips, no hairline flares from the cutting wheel, and no gouges from careless polishing. Damage introduced later — glass banged against a truck bed edge, or set down on grit — can create the same kind of stress concentration a bad fabrication edge does, regardless of how well the panel was originally made. This is why handling protocol on site (edge protection, padded transport, setting panels on clean blocking) matters as much as the fabrication step itself. It is a separate issue from the nickel sulfide phenomenon covered in our tempered glass breakage guide, which originates from an inclusion inside the glass rather than from the edge.

4. The fabrication sequence, and why the order is fixed

Annealed glass is cut to size, then every hole, notch and cut-out is machined, then the edges are finished to the specified profile, and only after all of that is the pane sent for tempering (or heat-strengthening) if the application calls for it. That order is not a convenience — it is a hard constraint. Tempering puts the outer surfaces of the glass into permanent compression and the interior into tension; that balance is what gives tempered glass its strength and its safe break pattern. Cutting, drilling or grinding a tempered pane afterward disturbs that balance and very often causes immediate or delayed breakage.

In practice, this means every measurement, every hardware position, every outlet and sconce location has to be confirmed before the glass is sent for tempering. A shop drawing approved at that stage is the last point where a change is simple; after tempering, the only fix is to fabricate a new piece.

5. Hole and notch placement constraints

Holes and notches cannot be placed anywhere on a pane without consequence. Fabrication practice keeps holes a minimum distance from edges and corners, sizes them appropriately relative to glass thickness, and avoids clustering multiple penetrations close together — all to avoid creating a new stress concentration near an existing one. Where hardware demands a hole position that conflicts with these constraints, the panel size, hardware choice or hole layout is adjusted rather than the constraint being ignored.

6. Polishing laminated makeups

Laminated glass — two or more panes fused around an interlayer — can be edge-polished, but the interlayer itself does not polish the way glass does, and a laminated edge can show a faint line at the interlayer even on an otherwise clean polish. This is normal and expected on laminated edgework and is worth knowing in advance if the edge will be closely visible, such as on a frameless door or a tabletop.

7. Heat-soaking as a separate process

Heat-soaking is a post-tempering process that holds finished tempered panels at an elevated temperature to trigger breakage in panels containing a nickel sulfide inclusion before they leave the factory, rather than after installation. It happens after tempering and does not change the edge finish or the fabrication sequence described above — it is an additional quality step some projects specify, discussed in more detail in our nickel sulfide guide.

8. Shaping, curves and radius corners

Radius corners, arched tops and full curved panels are all fabricated before tempering, the same as straight cuts and holes. Curved edgework generally takes longer on the edging machine and is worth flagging early, since it affects lead time more than it affects the finished look. Low-iron glass is frequently specified alongside shaped or highly visible edgework because standard glass carries a green tint that becomes more noticeable on a thick polished edge; low-iron glass keeps the edge closer to colorless.

9. Edgework, hardware and mounting

The edge finish a panel needs often depends on how it is held. Glass set into a U-channel or base shoe usually has a ground or seamed edge, since the channel conceals it and a polish there would be wasted. Standoff-mounted and point-fixed glass typically needs polished edges because the perimeter stays visible, and the hole positions for the standoffs are set relative to the edge with a defined minimum distance. Mirror mounting hardware — clips, channel, or standoffs — follows the same logic: the mounting method decided during layout determines which edge finish makes sense, which is why edge selection and mounting are discussed together rather than in sequence. See our mirror measurement and installation guide for how that plays out on mirror projects specifically.

10. Tolerance, inspection and site handling

Cut and edge dimensions are held to a defined fabrication tolerance, not to an exact nominal measurement — every fabricator's edging equipment has some allowable variance, and panels are checked against that tolerance before they leave the shop. On site, receiving inspection checks for edge chips or cracks introduced in transit, since a panel that left the shop sound can arrive damaged. Any edge damage found before installation is addressed before the panel goes in; damage found after installation is a different conversation, and one worth having with whoever installed the glass.

For the finish and mounting choices that most often come up on mirror and partition projects, see the custom mirrors and glass partitions service pages.

Questions we're asked most often

Can a hole be drilled in tempered glass after it's installed?: No. Tempered glass is under permanent internal stress, and any cutting, drilling or edge modification after tempering can cause the pane to break. All holes, notches, cut-outs and edge shaping have to be finished before the glass goes into the tempering furnace, which is why measurements and hardware positions need to be confirmed before fabrication begins.
What's the difference between a seamed edge and a polished edge?: A seamed or arrised edge has its sharp corner knocked off for safe handling but stays visibly ground and matte; it is a safety treatment meant to be concealed behind a frame, channel or trim. A polished edge is ground smooth and buffed clear, and it is meant to be seen — it is the standard choice for frameless work where the edge is exposed.
Does edge finish affect breakage risk?: Edge damage — nicks, chips and micro-fractures introduced during handling or a poor cut — is one of the more common origin points for glass failure, tempered or not. A clean, correctly finished edge with no surface damage handles stress far better than a rough or nicked one. This is separate from the nickel sulfide phenomenon discussed in our tempered glass guide, which originates inside the glass rather than at the edge.
Can curved or radius glass get any edge finish?: Most standard finishes — ground, flat-polished, pencil-polished — can be applied to curved and radius-cut edges, though curved work generally takes more time on the edging machine than a straight cut. Mitred edges are the exception, since a true mitre depends on two flat edges meeting at a controlled angle.