Short answer: Solvent cement won't bond acrylic to wood, metal, or glass; use clear two-part epoxy for small rigid joints, silicone for glass and seals, 3M VHB foam tape for panels (3M's rule is about 4 square inches of tape per pound of static load), or screws in oversize holes. Acrylic expands about 3 times as much as metal and 8 times as much as glass, so anything bigger than a few inches needs a flexible bond or room to move.
Why won't acrylic cement work on wood or metal?
Acrylic cement works by dissolving the surface of the acrylic so two pieces fuse. It doesn't dissolve wood, metal, or glass, so there's nothing for it to fuse with. You'll get a joint that pops off with a fingernail. For mixed materials you need an adhesive that grips both surfaces, or a fastener. Sheet makers go further: Plaskolite and Röhm both suggest considering mechanical attachment first, because bonds to dissimilar materials are harder to make and usually weaker than acrylic-to-acrylic joints.
Key facts
- Acrylic's expansion: about 0.00004 in./in./°F, roughly 3 times metals and 8 times glass (Acrylite).
- For different materials, Plaskolite says the adhesive "should remain somewhat elastic and not harden on aging," and hard-set cements should be avoided on glass because a rigid bond can crack the glass as temperatures change.
- 3M VHB tape: about 4 sq. in. of tape per pound of static (hanging) weight; clean with 70/30 isopropyl alcohol and water; press at about 15 psi; 50% strength in 20 minutes, 90% in 24 hours, 100% in 72 hours.
- Röhm's adhesive table for glass, wood, and metals lists one- and two-part silicones (a primer may be needed), double-sided tapes, foam tapes, and contact adhesives.
Which adhesive should you use?
| Adhesive | Good for | Watch out for |
|---|---|---|
| Clear two-part epoxy | Small, rigid joints: acrylic feet, knobs, metal inserts, a small panel set into wood | Rigid, so long joints can crack loose as acrylic expands. Some epoxies yellow in sunlight. Fast-set types are weaker. |
| Clear silicone (RTV) | Acrylic to glass, glazing into frames, sealing panels to metal, outdoor joints | Flexible, so it handles expansion, but it's weak in tension and isn't paintable. Plaskolite lists DOWSIL 732 RTV for acrylic to glass. Check the label for plastics compatibility and test on scrap. |
| 3M VHB acrylic foam tape (e.g. 4950, 0.045 in. thick) | Signs to walls, panels to metal frames, a clean alternative to standoffs | Needs clean, smooth surfaces, firm pressure, and 72 hours for full strength. Shows through clear acrylic. Porous wood must be sealed first. |
| MS polymer / hybrid adhesive | Larger panels on wood, metal, or masonry | Check that the label lists acrylic or plastics; test for crazing. |
| Screws, bolts, standoffs | Anything heavy, outdoors, or structural | Drill oversize holes and don't overtighten. See below. |
What glue should you not use on acrylic?
Acrylic is attacked by many solvents, which cause crazing: a web of fine cracks that can spread later. Acrylite's chemical table rates acetone, lacquer thinner, MEK, toluene, xylene, and methylene chloride as "not resistant." Avoid:
- Solvent-based contact cement and construction adhesives on visible faces (a strong solvent smell is the warning sign).
- Spray adhesives not labeled safe for plastics.
- Hot glue for anything that matters. It peels off smooth acrylic and lets go in heat.
- Glazing compounds or vinyl gaskets with plasticizers that can migrate into the acrylic.
When in doubt, put a dab on a scrap of the same acrylic, flex it slightly, and look at it after a day.
Why do big glued joints fail?
Expansion. Acrylic moves about 0.00004 in. per inch per °F; Acrylite puts it at 3 times as much as metals and 8 times as much as glass. Wood moves mostly with humidity rather than temperature, and acrylic also swells slightly with humidity (Acrylite measures 0.2% at 60% RH and 0.6% at 100% RH).
On a 4 in. part this hardly matters. On a 36 in. panel glued rigidly to a steel frame, a 60 °F swing moves the acrylic about 0.09 in. more than the frame. A rigid epoxy line can't absorb that, so the bond or the acrylic gives. Rules of thumb:
- Small parts (a few inches): epoxy is fine.
- Panels larger than about a foot: use a flexible adhesive (silicone, foam tape) or fasteners in oversize holes. Keep bonded areas as small as practical.
- Outdoors or in sun: plan for bigger swings. Work out the movement with the thermal expansion calculator.
More on this in acrylic thermal expansion.
How do you get a good bond?
- Clean both surfaces. Wash acrylic with mild soap and water and dry it. Degrease metal and glass; Plaskolite suggests roughening metal by sanding or blasting for a stronger bond. For VHB, 3M specifies a 70/30 isopropyl alcohol and water wipe; on acrylic keep it to a quick wipe, since sheet makers rate alcohol as limited resistance.
- Seal raw wood before using tape; 3M says porous surfaces need sealing to give a unified surface.
- Lightly scuff hidden areas of the acrylic for epoxy. Skip this for tape on clear parts where the scuff would show.
- Apply pressure. For VHB, press firmly (about 15 psi) with a roller; apply between 70 and 100 °F if you can.
- Wait for the cure before loading the joint: 72 hours for VHB, and whatever the epoxy or silicone label says.
When should you use screws instead?
For heavy or outdoor work, screws and bolts are the most reliable connection. Röhm's rule for hole size is bolt diameter plus 5 mm per meter of panel length, with the hole at least 1.5 hole diameters from the edge, and soft washers (EPDM, PE, or PTFE, never plasticized PVC). Plaskolite adds: cushion metal hardware with a rubber or cork gasket, use shoulder bolts, and don't bear countersunk screws directly on acrylic. Read can you screw into acrylic and how to drill acrylic without cracking. We can drill and countersink holes for you when you order through the instant quote.
Questions
Can I glue acrylic to a glass mirror?
Use silicone or a mirror-safe adhesive labeled compatible with plastics, in dabs or strips rather than a full rigid layer. Avoid anything that might attack the mirror backing, and leave room for the acrylic to expand.
What's the best way to set acrylic into a wood frame?
Cut a rabbet or groove slightly larger than the acrylic, and hold the panel with small clips, glazing points, or a bead of silicone so it can float. Gluing it solid with epoxy often leads to cracks as the wood and acrylic move.
Does super glue work for acrylic to metal?
For tiny parts, yes, but CA is brittle and its fumes can frost clear acrylic. Epoxy is the better choice for anything bigger than a small trim piece.
How much VHB tape do I need to hang an acrylic sign?
3M's general rule for static loads is about 4 sq. in. of tape per pound. A 2 lb sign needs at least 8 sq. in. of well-pressed tape, spread out, and 72 hours before it's at full strength. For anything over a doorway or walkway, add mechanical fasteners.