Museum Glass vs Optium Museum Acrylic: Which Should You Choose?

Museum Glass and Optium Museum Acrylic give the same protection: both are made by Tru Vue, both block up to 99% of UV light and both carry an anti-reflective coating. Choose Museum Glass for most framed work up to around A1, and choose Optium when the piece is oversized, needs to travel, hangs somewhere breakage is a risk, or is a pastel or charcoal that static could disturb.

So the real decision is not about protection. It is about weight, breakage, static and sheet size. This guide sets out the published specifications side by side, explains when each one wins, and shows how we specify glazing in a quote at the workshop.

Museum Glass vs Optium at a glance

Two points stand out. The UV figures are identical, so neither option protects colours and paper better than the other. And the reflection figures are both very low: under 1% for Museum Glass and under 1.6% for Optium, against the 8% Tru Vue quotes for its uncoated Conservation Clear. In a normal room, both read as close to invisible.

What both products have in common

• Conservation-grade UV protection. Tru Vue rates both at up to 99% of UV in the 300 to 380 nm range, and both pass the ISO 18916 Photographic Activity Test and meet ISO 18902, so both count as photo-safe.

• An anti-reflective coating on both sides, which is what removes the glare you see on ordinary picture glass.

• Permanent UV protection. On Museum Glass the UV coating is bonded into the glass surface; on Optium the UV filter is part of the acrylic itself. Neither wears off with age or cleaning.

If you want the wider picture on UV glazing, including the cheaper Conservation Clear and Artglass UV92 options, our guide to UV protection in picture framing compares all four.

When Museum Glass is the better choice

Museum Glass is our default for valuable work in normal domestic or gallery conditions, typically up to around A1. It is 2.5 mm glass, so it is rigid, it lies flat with no ripple, and its surface is naturally harder than any acrylic. For a watercolour, a signed print, an antique map or a family photograph in a standard-sized frame on a living room wall, there is rarely a reason to look further.

• Frames of a normal size, where the weight of glass is not a problem for the frame or the wall.

• Work that will stay on one wall rather than travel.

• Prints, photographs and works on paper that are not loose or powdery on the surface.

When Optium Museum Acrylic is the better choice

Tru Vue recommends acrylic wherever weight, safety or movement is a concern, and that matches what we see in the workshop. Optium is the right call in four situations:

• Oversized work. A single Optium sheet goes up to 1830 x 3050 mm, against 1220 x 1725 mm for clear float Museum Glass. Acrylic is also much lighter than glass, which matters for large frames, fixings and handling. Our oversized framing work often uses it for this reason.

• Work that travels, such as pieces lent to exhibitions or moved between homes and offices. Optium is shatter resistant, so a knock in transit does not put broken glass against the artwork.

• Public and high-traffic spaces: receptions, corridors, hospitality and healthcare settings, children's rooms, and anywhere a falling frame could hurt someone.

• Pastel, charcoal and other friable or static-sensitive work. Ordinary acrylic carries a static charge that can lift loose pigment off the paper. Optium is anti-static, and Tru Vue lists pastels, charcoals, textiles and lightweight papers among its intended uses. Tru Vue also says Museum Glass may not be the best choice for friable materials.

For the general trade-offs between the two materials across all grades, not just the museum tier, see our acrylic vs glass guide.

Sheet size, and what happens above it

Clear float Museum Glass tops out at 1220 x 1725 mm, and the low-iron Water White version at 810 x 1015 mm. Above that size, glass is no longer an option in a single sheet. Optium goes to 1830 x 3050 mm in a single sheet, and Tru Vue says seamed Optium, where two or more sheets are joined, can reach around 3 m x 7 m for very large works. Optium also comes in 3.0, 4.5 and 6.0 mm thicknesses, so thicker sheet can be used where a large span needs more rigidity.

Cleaning and care

Both are easy to keep clean, but they are not cleaned in quite the same way.

• Museum Glass: Tru Vue describes the surface as durable and easy to clean. Use a soft, clean cloth and a glass cleaner, and do not use anything abrasive on the coating.

• Optium: Tru Vue says to use a common household glass cleaner, and specifically not acrylic cleaners or polishing agents. It has a hard coat against scratches, but it is still acrylic, so use a soft cloth and avoid gritty dusters. Because it is anti-static, it attracts far less dust than standard acrylic in the first place.

How we specify glazing in a quote

When you send us a piece, the glazing line in the quote comes from four questions: how large is it, where will it hang, will it move, and what is the surface like? If the answers are a normal size, a domestic wall, staying put and a stable surface, we will usually specify Museum Glass. If any answer points to size, safety, travel or a friable surface, we will specify Optium and say why.

Both sit at the museum-grade level of framing. If you are deciding between conservation and museum-grade framing more generally, our guide to conservation vs museum-grade framing explains the difference, and our conservation framing service covers how we handle valuable work at the Bollington workshop.

Tell us the piece, size and where it will hang, and we will recommend the glazing in your quote.