When mounted on their appropriate bases, plastic-backed and steel-backed photopolymer plates both create type-high surfaces for letterpress printing. Both plate types are recyclable. We’ll talk about some of their differences below.
Plastic-backed polymer plates are flexible, transparent, easy to cut, and mount onto a Boxcar Base for simple registration. You’ll find these plates:
- can be cut with scissors in both their unexposed and exposed forms.
- are transparent, meaning you can see the Boxcar Base’s grid through your plate. This allows for simple alignment of your plates to your base: For perfect registration, align a certain element of your plate to the grid: take a horizontal or vertical element in your plate (this could be your registration marks, or a horizontal line in your artwork) and line it up to the grid.
- eliminate plate creep (steel-backed plate users sometimes experience this while on press). The plastic-backed plate’s adhesive is shift resistant, giving you a secure, strong hold during printing (but the adhesive also peels up easily when you’re done printing)
- allow printers to print two color jobs using one plate if the design elements don’t touch. Cut out the second color images/text with a craft knife or scissors and set aside. Print color #1. Set your second color images back in place and pull up the first plate for color #1—perfect registration!
- allow designs to be ganged up on plates closely to save space (and money).
- are reusable. You will be able to reuse the plate many times if you keep the adhesive protected with the blue overlay after printing. You can also replace adhesive for even more extended plate use.
- more prone to curling, especially with large solid areas over time.
- If purchasing unexposed plastic-backed polymer plates, you’ll also want to purchase film adhesive to adhere your plates to your base. If we’re making your plates for you, we include adhesive.
- are suitable for metal clay jewelry.
- Over here at Boxcar, we use plastic-backed plates for all our printing (the Jet 94 Clear plate paired with the Standard Boxcar Base).
Steel-backed polymer plates are compatible with magnetic bases, generally the Patmag or Bunting base. Steel-backed polymer plates:
- require cutting with a metal shear or heavy-duty trimmer. You can use tin snips, though you may end up with kinks in your plate, as tin snips won’t cut as cleanly.
- sometimes shift and creep on your base during printing. Magnets in the base effectively hold a plate from peeling but cannot always hold a plate from moving side to side. The cylinder or rollers of a press can move steel-backed plates out of register (that’s “plate creep”).
- are not transparent. Because magnetic bases aren’t gridded (and you can’t see through these plates), you’ll have to align your plates to your base with a line gauge and possibly registration marks. This works, but it is more time consuming and there’s more room for error.
- are rigid, meaning they don’t bend well. This inflexibility can cause plates to kink and warp when handled so that their corners may work up while on press. Steel-backed plates are, however, very durable and not prone to curling over time.
- can be more expensive than plastic-backed plates because you may require registration or crop marks which makes for a larger plate.
- are difficult to get on and off the base, especially when the base has inlaid magnets. When placing metal plates on a magnetic base, keep fingers clear so they don’t get pinched when the magnet grabs. When taking your plate off the base, try an ink knife to pry under the plates to release from the magnetic base.
- have sharp edges, which dictate extra care when handling.
- can be used for a wide range of printing and impression—on leather, metal clay jewelry, ultra heavy-weight paper stocks. Steel-backed plates can also be used on etching presses when relief printing is desired. They are not suitable for high temperatures of foil stamping though.