Both materials are transparent, both are sold as “clear”, and buyers compare them on price per square metre. That misses everything that decides whether a case survives three years on a dresser. These are the differences that show up once the case is in the room.
Weight decides where the case can live
Cast acrylic has a density around 1.19 g/cm³. Soda-lime glass sits near 2.5 g/cm³, so a glass panel of the same thickness weighs roughly twice as much. On a 500 × 400 × 400 mm case that is the difference between a box one person carries and a box two people lift with care.
Weight then becomes a design constraint. A wall-mounted case has to transfer load into studs or a plywood backer, and every extra kilogram is more anchor. A glass case of any real size usually needs a frame to carry the panels; the frame handles the weight and also changes the look. Acrylic gets its stiffness from the sheet and the joint, so the corners can stay empty.
For a shelf of 1/6 figures or a wall of blind boxes, that is the whole argument.
Light transmission is close; the edge is not
Clear cast acrylic transmits roughly 92% of visible light; standard clear float glass sits a little lower, around 90%, and low-iron glass closes the gap. In a lit room you will not see that difference. What you see is the edge.
Acrylic has no green edge and carries light along the sheet, which is why an edge-lit acrylic case glows at the perimeter and a glass case under the same LED strip does not. If the design depends on a lit outline, the material is already decided.
Reflection behaves the same way in both. A glossy panel in front of a bright window is a mirror whatever the material, and the fix is angle and lighting position.
UV protection is a spec, not a material
Neither material protects a collection by default. Ordinary glass blocks most UV-B and passes a large share of UV-A, which is the part that fades inks and yellows some plastics. Standard acrylic passes UV-A as well, though it cuts off further into the UV-B end than glass does.
Protection comes from a grade: acrylic sheet with a UV-absorbing additive, or laminated glass with a UV film in the interlayer. We use a UV-filtering film on the modular range and quote it as a layer rather than a promise, because the number only holds for the film supplied. If a signed print is going into a south window, ask for the UV figure and which component carries it.
Scratches: glass wins, and it matters less than buyers think
Glass is harder. On the Mohs scale it sits around 5.5; acrylic is around 3, close to a copper coin. A ring, a car key or a child's toy will mark acrylic and leave glass untouched. That is a real difference and it is the strongest argument for glass in a high-traffic retail position.
The counter-argument is repair. An acrylic scratch can be polished out with a compound and a soft pad, on site, and the panel goes back to clear. A scratched glass panel is replaced. For a collector who will own the case for a decade, a repairable surface often beats a harder one.
The exception is daily wiping with a dry cloth across the same path, which hazes acrylic over a couple of years. Use a microfibre cloth and a spray and the haze does not build.
Joints: bonded corners or a frame
Acrylic can be solvent-bonded. Two machined edges are joined with a solvent that softens the surfaces and lets the polymer chains merge, and the result is a corner with no visible fastener. That is why an acrylic case can be a clean box with a lift-off lid or a magnetic door.
Glass cannot be bonded that way. It is held by a frame, by structural silicone, or by UV-cured adhesive in a mitred joint that needs a jig and a clean room. Frameless glass cases exist and they are beautiful; the frame or the adhesive becomes the engineering, and the cost moves with it. A glass box with a hinged door needs metal at the hinge line. An acrylic box puts the hinge in the sheet.
The joint also decides how tight the case can be. A bonded acrylic case with a magnetic door closes to under a millimetre and still opens easily. A framed glass case closes against a gasket, and gaskets have a thickness.
Movement, and why acrylic needs clearance
Acrylic moves about seven times as much as glass for the same temperature change. A 600 mm panel that is comfortable in a 20 °C room will have grown by roughly half a millimetre at 35 °C. That sounds trivial until the panel is captured in a rebate with no clearance, which is when it bows or cracks at a corner.
Glass moves too, just less, and it does not forgive a tight fit. The practical rule is the same for both: never trap a panel on all four edges with zero gap. Leave a millimetre or two.
Heat is the other side of it. Acrylic softens near 100 °C and loses stiffness well before that, so a case under a hot halogen fitting will sag where glass would not. With LED lighting at a sensible distance, it is a non-issue.
Cleaning chemicals matter more than cleaning frequency
Ammonia-based glass cleaner and alcohol-based sanitiser are the two things that quietly ruin acrylic. Both attack the surface and can produce fine crazing that looks like a spider web under a light. Once that happens it cannot be polished out.
Acrylic wants water with a drop of mild soap, a microfibre cloth, then a dry pass. Glass takes ammonia cleaner without complaint. If the case goes into a store with a contracted cleaning crew, send their product list with the order, because that is where the damage starts.
Fire, public space and the rule nobody reads
Acrylic is a combustible thermoplastic. It ignites, it burns, and it drips. Glass does not burn. In a museum vitrine, a hotel lobby or a shopping centre, that difference is written into the fire strategy for the building and can override every other argument here.
For a home collection it rarely matters. For a retail fixture, ask the venue before the material is ordered. We have quoted a case twice because the first version was right for the product and wrong for the building.
Which one to specify
| Situation | Material that usually wins | Why |
|---|---|---|
| Home shelf, wall-mounted, light figures | Acrylic | Half the weight, no frame, screws into a bracket |
| High-traffic retail counter | Glass, or acrylic with a replaceable front | Abrasion from keys, rings and handling |
| Edge-lit outline, printed panels | Acrylic | Carries light at the edge; takes direct print and film |
| Signed prints and boxed collectibles in daylight | Either, with a stated UV grade | Protection comes from the additive or interlayer, not the base material |
| Museum vitrine, listed building, hotel lobby | Glass | Non-combustible, harder surface, accepted by fire strategy |
| Ships flat, assembled on site | Acrylic | Bonded or knock-down joints; glass needs a frame |
Where glass is the right answer
Glass is not the compromise option. For a permanent public display, a heavy object, or a surface that gets knocked, glass is the correct specification and acrylic is the saving. The reason our own range is acrylic is narrower: collectors want a case they can hang and move without a frame, and brands want printed panels and lit edges inside one bonded box.
If the brief includes a fire officer, a listed interior or a 30 kg object, say so at the start. We would rather quote glass than let the venue reject acrylic.
What to send before the material is chosen
- The object's height, width, depth and weight, with the heaviest single item named
- Where the case will sit: shelf, wall, counter or floor
- Whether it will be cleaned by a contractor, and with what
- Daylight exposure and which direction the window faces
- Whether the venue has a fire or materials requirement
- Whether the case ships assembled or flat
Those six answers settle the material before anyone argues about price. For the panel thickness that follows from them, read the thickness guide; the modular range that uses both approaches is on the MODU-BOX page. If the venue rule is unclear, send the requirement through the project enquiry form and we will mark which parts of the build it changes.