Prepare the artwork,
not just the film.

What the separation actually needs from your file

Spot colour separation works by sorting pixels into ink groups by colour family, not by counting how many colours a file technically contains. A clean scan or a flat illustration with five distinct hues separates predictably. A photograph with thousands of gradually blending shades does not — there is no "correct" place to draw five boundaries through a smooth gradient, so the tool draws one, and it may not be where you would have drawn it.

Three things decide how predictable your result is, before you touch a single setting in the tool:

• Colour count. Aim for artwork with a countable number of distinct colour families — a logo, a flat illustration, a poster — rather than a photograph. Set your ink slider to match roughly how many colours you can actually see.
• Contrast between colours. Two colours that are close in both hue and lightness invite the clustering to merge them, or to flip pixels back and forth at the boundary. Leave real daylight between any two colours you want to stay separate.
• File format. Save as PNG, not JPEG. JPEG compression blurs colour boundaries, and those blended edge pixels get assigned to the wrong ink during separation.

Resolution matters too: aim for 300 PPI at your final print size. That is roughly 3000 pixels on the long side of a 10-inch print, or about 3500×4960 for an A3 sheet. The classical rule of thumb (image resolution ≈ twice your line frequency) would allow far less, but 300 PPI protects hard edges, type and fine linework, not just the halftone dots.

Match your detail to your mesh count

If you are heading for a screen, the mesh sets a hard floor on how small a detail can be and still survive wash-out. The same mesh presets the tool ships with:

Before you separate, check your type size and line weight against the smallest-dot column for the mesh you plan to use — anything finer will not hold. The tonal range column matters just as much: near-white highlights and near-black shadows outside that range get clipped by design, because dots that fine or that dense cannot survive your screen. That clipping is deliberate, not a bug in the tool — decide before you separate whether your source needs brightening or darkening so the detail you care about sits inside that range. Full numbers and the paper equivalents are in the mesh count to LPI chart.

Design for the knife, not the mesh (lino and block printing)

Relief printing removes the mesh entirely, and with it, halftone shading. With the raster off, the tool decides every tone at the 50% mark: anything at or above becomes a solid shape, anything below becomes blank. A soft gradient in your source file turns into one hard edge, wherever your midtone happens to fall.

That is worth controlling before you separate, not after. Adjust levels or contrast in an image editor so the 50% cutoff lands where you actually want the carved edge to be, rather than leaving it to whatever midpoint the file happens to have. If a gradient matters to the finished print, the relief answer is more flat layers, not more tone in one layer: three tints of the same colour printed as three separate shapes read as a gradient from arm's length.

Two checks specific to relief work:

• Floating islands. If your design has a shape enclosed inside a cut-out area, it needs a bridge connecting it to the rest, or it falls out when you cut. Check for these visually before you carve.
• Mirroring. A block prints mirrored, so whether your carving guide should be mirrored or not depends on how you plan to transfer it to the block.

Both are covered in full, along with registration between blocks and the difference between multi-block and reduction printing, in the lino and block printing guide.

A pre-separation checklist

Common questions

We are new, and reviews, testers and ideas make this better. Write a review · Become a tester · Send an idea · Show us your work