Mixing
Slab

The short version

You choose a colour. The tool searches through the possible combinations of your inks, works out what each one would actually look like once mixed, and shows you the closest it can get — as percentages, as grams for your batch size, and as a ratio you can knife out by eye.

Choosing a colour

• Wheel — the traditional twelve-hue artist's wheel. Four rings: the pure hue, its tint (plus white), its tone (plus grey) and its shade (plus black). Click any cell.
• Spectrum — a continuous disc for colours that don't sit neatly on the twelve, with a lightness slider underneath.
• Swatches — forty named colours grouped into families, plus any you have saved yourself.
• Hex — paste a code, or use the picker to sample anything on screen.
• Image — load a picture and click it to lift a colour from a photograph, a fabric, a bit of packaging, anything.

The example

Try an example on the Image tab loads The Great Wave off Kanagawa by Katsushika Hokusai, about 1831. It is a good thing to practise on — a handful of strong, flat colours that were themselves printed one at a time from woodblocks. Click the deep blue of the wave and see what your inks make of it.

The print is long out of copyright and the Metropolitan Museum of Art has released its scan into the public domain, so it travels with the tool and works with no signal.

Colour relationships

On the Wheel tab, the buttons under the disc show the classic harmonies, drawn in the middle exactly as the dial on a printed colour wheel does — a line for complementary, a triangle for a triad, a square for a tetrad. Related hues get a tick on the rim and appear as chips you can click straight into the mixer.

Reading the result

The two squares at the top butt together with no gap between them, which is the fairest way to judge a colour difference: if you can't see the join, it's a good match.

Underneath is a verdict and a number. The number is ΔE — a measure of how different two colours look to the human eye, not how different their codes are.

Below the recipe, other ways to get there lists alternatives using fewer inks. Sometimes a two-ink mix at ΔE 3 is worth more to you than a five-ink one at ΔE 0.5.

Your inks

Open the panel at the bottom to build the set to match your shelf. Rename an ink by typing over it, remove one with ×, or add from the library. Two minimum, twelve maximum.

Two settings per ink matter. Colour should be your real ink, not a guess — print a solid swatch, photograph it in daylight and sample it. Strength is how far that ink goes in a mix: if recipes keep coming out too weak in blue, raise blue's strength; too strong, lower it. This is what turns a decent approximation into something tuned to your studio.

Palettes

A palette is one set of inks and what they are printed on. Save as many as you like and switch between them: one for oil-based relief work, another for a water-based set, another for the same tubes on a different paper. Calibration lives inside each ink, so it travels with the palette rather than following an ink name around. Everything saves as you go — there is no save button — so duplicate a palette before you start pulling it apart.

The library holds common relief colours and the Cranfield Traditional Etching range, with product codes so you can match a tube. Pick the ones you actually own; a palette full of inks you do not have produces recipes you cannot mix. Those Cranfield figures are sampled from the printed colour chart, which shows each ink at full strength as a reproduction, not a measurement. Treat them as a starting point and calibrate. Extender, Transparent Lake White, Silver and Gold are missing on purpose — the first two read as bare paper and would be mistaken for white, and metallics do not behave like pigment in a mix. Note too that the five blacks are all but identical on a chart, however differently they behave under a burnisher.

You can also pick a colour off a photograph and add it as an ink rather than as a target. That is how you get an ink set nobody publishes a chart for: print your own swatches, let them dry properly, photograph them flat in daylight, and sample those. Water-based inks especially dry a good deal lighter than they look wet, so sampling a wet slab will overstate every ink you own.

If a palette has no white in it, the tool says so. It cannot mix a pale tint from inks that are all dark — in water-based printing you would thin the ink or print a thinner film and let the paper do the lightening, which is outside what this calculator models.

The palette link encodes the whole set into a URL, so you can send someone a link that opens the tool with those inks already set up. It arrives at their end as a new palette rather than replacing anything. It is also the only real backup: saved palettes live in this browser alone, but a link you have emailed yourself survives anything.

Recipe book and saved swatches

When a mix comes out right, name it and save it. Each entry becomes a palette-knife daub in the mixed colour, with the exact percentages recorded, so you can pull the same colour again for a reprint months later. Clicking an entry reloads that colour — note that it re-solves against your current inks, so if you have swapped a tube since, you will see both what you mixed then and what you would mix now.

You can also save any colour as a named swatch, which appears under "Yours" at the top of the Swatches tab.

The maths, briefly

Screens mix light: red and green make yellow. Ink does the opposite — each pigment subtracts part of the spectrum, which is why red and green ink make mud. So the tool models each ink by how much it absorbs versus scatters in each channel, mixes those absorption figures rather than the colours themselves, and converts back. It's the standard Kubelka–Munk approach, simplified.

Finding the recipe happens in two passes: a first sweep through every whole-number split of the parts across your inks, then a fine adjustment that nudges the amounts until the match stops improving. Closeness is scored in a perceptual colour space, so it optimises for what your eye sees rather than what the numbers say.

What it can't do

• Reach every colour. Red, green and blue are poor subtractive primaries. Bright cyans, clean oranges and anything magenta are out of range without a real cyan and magenta on the shelf. The tool tells you rather than pretending.
• Account for your paper. Recipes assume ink at full opacity. On toned or unsized paper, or thinly inked, results will read lighter and warmer than predicted.
• Model transparent base, extender or overprinting. Those change the rules entirely.
• Replace a test proof. Screens are lit from behind and paper is not. Mix a little, pull a proof, adjust, then save what worked.

Where your data lives

Everything — inks, swatches, recipe book — is stored in your own browser and never sent anywhere. Clearing your browser data will clear it too, so if a palette matters, copy its link.

Putting it on your phone

This is a proper installable app, not just a bookmark. Tap Install app at the top and it goes on your home screen with its own icon, opens full screen with no browser furniture, and — the useful part in a studio — keeps working with no signal at all.

On an iPhone or iPad the button shows you where to find it instead: Safari puts Add to Home Screen behind the Share button.

Your inks, swatches and recipe book carry over, because the installed app uses the same browser storage as the tab you installed it from.

Thank you

This is free and always will be. If it saves you some ink and some swearing, you can buy the creator a coffee.