ColorLayers
Underbase: when you need one and how much to choke
On a dark garment a colour ink does not read the way it does on white: the material shows through and pulls every shade towards itself. An underbase is the layer that stops it.
What it is for
Textile ink is semi transparent. Laid straight onto black, red goes maroon, yellow goes green, and the light tones disappear almost entirely. A base gives the colour inks something pale to sit on, so they land the way you saw them.
It is not free. Another screen, another pass, another flash, and a stiffer hand on the finished shirt. So the question is not whether to lay one but exactly where it is needed.
Two modes
- Solid. One flat layer under everything that prints on top. Predictable, the most opaque, the most ink.
- Following coverage. The base carries the tone of what sits on it: denser under pale areas, weaker or absent under dark ones.
The second saves ink and gives a softer print, but it asks that registration be in order: wherever the base thins out, a misregistration shows immediately.
The threshold, where the base stops printing
Coverage is totalled across every ink, and below a set level the base does not print at all. The reasoning is that scattered dots in a sparse halftone do not need white under them: it adds nothing there and prints as a grey haze around the dots.
The threshold is yours to set. Raising it leaves more fabric open and softens the print; lowering it buys safety with opacity.
Choke, and what it costs
Choking is geometry: the base is pulled inward so the colour inks cover its edge and no white shows around the outline. It is set in millimetres, because the amount depends not on the artwork but on how accurately the press registers.
A choke is never free. Everything taken off the base is a run of pixels where colour ink will land on bare garment, and there it loses its colour again. So those pixels are counted and shown as a number: when it climbs, the choke is too much for this artwork.
Start from what your press holds rather than from a round figure. Half a millimetre on a tight press and half a millimetre on a worn one are not the same half millimetre.
A base does not have to be white
Any ink in the palette can take the role. On artwork built from beige it makes more sense to base it in beige than to add an eighth screen for a white that is not in the original at all.
The reverse holds too: nothing adds a base on your behalf. Print three inks on a light garment and the separation stays three inks.
FAQ
Does dark fabric always need a base?
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No. A solid block of dark ink on a dark garment manages without one. It is needed where there are pale tones and halftones, which is exactly what the material eats.
How much choke?
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As much as your registration wanders, plus a margin. The check gives you the bearing: the count of uncovered edges tells you when you have gone too far.
Can I see the print without a base?
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Yes, the preview shows both on your chosen garment colour. It is the quickest way to settle whether one is needed here at all.
