Walk into any plastics supplier and you’ll find two types of clear acrylic sheet sitting side by side. They look identical. They’re both transparent, both lightweight, both called acrylic. But they’re made differently, they behave differently when you work with them and they suit different jobs. Picking the wrong one won’t be a disaster, but picking the right one saves you time, money and frustration.
How They’re Made (and Why It Matters)
Cast acrylic is made by pouring liquid acrylic between two sheets of glass and letting it cure slowly. This slow process creates a denser, harder material with excellent optical clarity. The surface resists scratching better and polishes to a higher shine. It also machines more cleanly, giving you smoother edges when you cut or drill it.
Extruded acrylic takes a faster route. Acrylic pellets are melted and pushed through rollers to create sheets of uniform thickness. The speed of production brings the cost down, which is why extruded acrylic is typically 20-40% cheaper than cast. The trade-off is a slightly softer surface that scratches more easily and can be more prone to stress cracking around drill holes or tight cuts.
Where Cast Acrylic Wins
If optical perfection matters to your project, cast is the way to go. Picture framing for valuable artwork, high-end retail display cases, museum exhibits and any application where people will be looking through the acrylic at close range. The clarity difference is subtle but real, and it holds up better over years of use.
Laser cutting and engraving also favour cast acrylic. It produces cleaner, frost-white edges when laser cut, which is why signmakers and fabricators prefer it. If you’re making illuminated signs, award plaques or decorative pieces where the edge finish is part of the design, cast is worth the premium.
It also performs better for heat bending. Cast acrylic has a wider forming temperature range, which gives you more control and a lower risk of bubbling or distortion. For anyone doing thermoforming work, this makes a genuine practical difference.
Where Extruded Acrylic Wins
For the majority of practical projects, extruded acrylic does everything you need at a lower price point. Secondary glazing, greenhouse panels, shed windows, sneeze screens, simple signage and protective covers all work perfectly well with extruded sheet. The optical difference is negligible for these applications and the cost saving adds up quickly, especially on larger orders.
Extruded acrylic also has more consistent thickness across the sheet. The roller process ensures uniformity, which matters if you’re fitting multiple panels side by side or working to tight tolerances. Cast acrylic can vary slightly in thickness across a single sheet due to the curing process, though this is rarely noticeable in practice.
Quick Comparison
In terms of clarity, cast scores marginally higher but both offer over 92% light transmission. For scratch resistance, cast is noticeably harder. Price favours extruded by a significant margin. When it comes to machining, cast gives cleaner cuts and polishes more easily. For laser work, cast produces superior frosted edges. Thickness consistency is slightly better with extruded. Both types offer the same UV stability and weather resistance, making either suitable for outdoor use.