Repair guide
How to bond a PETG 3D-printed part to glass
Glass bonds well chemically but has no surface for a mechanical key, so the joint depends on a scrupulously clean, dry surface and an adhesive that stays put. A clear two-part epoxy is the practical choice.
The short answer
Clean the glass with isopropyl alcohol until it is genuinely grease free, abrade the PETG print, and bond with a clear two-part epoxy. Glass is the fussiest half: a fingerprint is enough to halve the strength, and any moisture at the surface will find its way into the bond line over time. If the joint will be in daylight, use a UV-stable epoxy or expect it to yellow.
- Difficulty
- Moderate
- Time needed
- 20 minutes work, 24 hours cure
- What you need
- Clear two-part epoxy, isopropyl alcohol, lint free cloths, 180 grit abrasive, masking tape or modelling clay, sharp blade, gloves
Glass is unusual. Most substrates need roughening, but glass is chemically receptive and a clean surface bonds well as it is. What it cannot tolerate is contamination. Skin oil, glass cleaner residue and airborne dust all leave a layer between adhesive and glass, and because there is no mechanical key to fall back on, that layer is the whole joint.
It is also worth knowing that glass bonds slowly lose strength in humid conditions. Water migrates along the interface and displaces the adhesive, which is why a glass joint that seemed strong can be pushed apart after a couple of damp years. Keeping the joint out of standing water and sealing its edges slows that considerably.
PETG is the easy half. It has a good surface energy for bonding, and its printed layer lines give epoxy something to key into once lightly abraded.
The practical trade off is appearance. Epoxy on glass is visible from the other side, so use a clear grade, mix it carefully to avoid bubbles, and keep the bonded area neat, because any squeeze out will show.
Step by step
- Wash the glass with hot water and detergent, rinse well, and dry with a lint free cloth.
- Wipe the bonding area with isopropyl alcohol and do not touch it again with bare fingers.
- Abrade the print's bonding face with 180 grit and wipe it with isopropyl alcohol.
- Dry fit and work out how you will hold the part while it cures. Tape or modelling clay both work.
- Mix a clear two-part epoxy slowly to avoid whipping air into it.
- Apply a thin even layer to the print, not to the glass, keeping 2mm in from the edges.
- Press the part onto the glass, hold for two minutes, then support it so it cannot slide.
- Leave 24 hours, then trim any squeeze out with a sharp blade held flat to the glass.
What to avoid
Do not touch the cleaned glass with bare fingers. One print is enough to weaken the joint noticeably.
Do not use glass cleaner. Most leave a residue designed to repel water, which repels adhesive too.
Do not expect a glass bond to survive permanently in a wet environment. Water works its way along the interface over time.
Never rely on an adhesive bond to glass for anything load bearing or overhead. Glass fails suddenly and the bonded joint can let go without warning. Wear gloves with uncured epoxy and take care with any glass edge.
The full bonding guide
Everything about gluing PETG to Glass
Last reviewed 13 September 2026.