Magnesium plates vs. letterpress bases – which is better?

Here are some differences you’ll find between the Boxcar Base system and magnesium plates. Maybe try a free polymer plate sample from us to dip your little toe in the water.

This is a magnesium plate.

This is a Boxcar Base, a type of letterpress base

detail.

The 94FL photopolymer plate (paired with the Standard Boxcar Base) can hold a 2 point Times New Roman or a .25 point isolated line.
Magnesium plates hold less detail: they can hold a minimum of 6 pt Times New Roman or a .25 point line.

mounting material.

Photopolymer plates are not permanently mounted to a printing base. With polymer, you purchase a reusable printing base that locks up in your chase. Magnetic bases pair up with steel-backed plates. The Boxcar Base pairs up with plastic-backed plates. These printing plates create a type-high surface when mounted temporarily onto the base. The Boxcar Base is a 100% aluminum base guaranteed to within 0.001″ in thickness, parallel, and flatness: this is flatter than many press beds in fact.
Magnesium plates are permanently mounted to wood to create a type-high surface. Accurate inking of wood-mounted plates is very difficult. Wood warps with changes in humidity conditions. Using wood as a base requires a lot more make-ready than polymer.

maintenance and storage.

If you store your polymer plates in a ziplock bag in a cool, dark place, your plates will last for years. Because you’re just storing the plates, not the base, polymer plates take up very little storage space—they can be stored in places like a file cabinet. Photopolymer needs no extra oils for storage.
After printing magnesium plates, you’ll have to coat them with an oil—such as Vaseline or vegetable oil—or else the plate will oxidize over time and render the plate unusable. Most magnesium plates are mounted on wood. If you get carried away oiling your plate, the extra oil can sink into the wood and potentially warp the wood bases. Because you must store both the plate and the permanent wood base, magnesium plates take up more storage space than polymer.

environmental impact.

Photopolymer plates are processed in water, which afterwards is safe enough to pour down the drain. Photopoylmer plates are recyclable.
Magnesium plates require acids to etch the plate, which isn’t great for the planet. You can recycle magnesium plates.

technical printing help.

We offer free letterpress help to all our customers, whether you’ve ordered our base, had us expose your polymer plates, or purchased unexposed photopoylmer from us to process yourself. We want to make sure our materials are working well on your press. Just call, email, or chat if you’re on press with a problem. We’re the largest letterpress shop in North America and we love helping other printers out.
Magnesium plates are very well suited for hot-foil stamping—they heat up more quickly and evenly and require a shorter dwell time, which is all great for foil. Because of this, most business for magnesium plate vendors comes from hot foil stampers, not letterpress printers. Ask your magnesium plate vendor about what kind of letterpress help they offer if you’re having trouble on press so you can compare.