Colour Drift Between Batches: Catching It Before the Client Does

Ask three people what colour a sack of snow powder is and you will get three answers: white, off-white, and ‘a bit beige’. None of them is describing the same thing, because the colour of the dry powder and the colour of the hydrated material are two separate questions, and the second one depends as much on the water as on the polymer.

That distinction matters most when a build spans two deliveries. Batch A goes down on Monday, batch B arrives on Thursday, and by Friday there is a visible seam across the display that nobody can explain to a client who is standing in front of it.

Where the colour actually comes from

The polymer itself is translucent when wet. What you see as white is light scattering off the surface and off the boundaries between granules, which is why a coarser grind looks brighter than a fine one and why a wet mix looks duller than a dry one. Add water with a high iron content and the scattering picks up a yellow cast; add water from an old galvanised tank and you get a grey one.

So the first suspect in any colour complaint is the water supply, not the powder. Two builds in the same town, one from a mains tap and one from a stored tank, can look like two different products. Before you blame a supplier, fill a clear glass from the tap you used and hold it against a sheet of white paper. Half the time the answer is in the glass.

The three-batch wall test

When a new delivery arrives, hydrate a small amount from it beside a small amount from the batch already on site. Put both in shallow trays, side by side, on a white surface, and look at them under the lighting the display will actually use. Daylight through a window is not the same as a 3000 K spot, and a difference that is invisible at noon can be obvious at eight in the evening.

Do this before the material goes into the build, not after. Fifteen minutes and two trays will catch most drift, and it is a far easier conversation with a supplier than a complaint about a finished display. Photograph the two trays with a batch card between them and keep the image; it is the only evidence that will settle an argument three weeks later.

When drift is real and when it is not

Some variation is normal and unavoidable between production runs. A slight shift in tone across a large area is invisible to a customer and obvious to the person who installed it, because they know where the join is. If the seam reads at two metres in normal light, it is a problem. If it only reads when you crouch down and look along the surface, it is not, and replacing a batch will not fix the way human eyes work.

The exception is a display lit from one side. Raking light exaggerates tonal differences along the direction of the beam, so a seam that runs parallel to the light is far more visible than one that runs across it. If you have two batches and no choice, orient the join across the light rather than along it, and feather the boundary over 40 cm rather than butting it.

What to do about a delivery that is genuinely off

Record the batch number, the date, and the water source used. Hydrate a sample and photograph it next to a reference under fixed light. Then call the supplier with those three things in hand, because a complaint that arrives as ‘it looks yellow’ goes nowhere and a complaint that arrives with a batch number and a reference photograph gets a technical answer within a day.

Keep a teaspoon of dry powder from every delivery in a labelled bag for the season. It costs nothing, it takes a minute, and it turns ‘the last batch was different’ into something you can demonstrate.

The reference card and the two-tray method we use for incoming checks are described in the artificial snow user guides, along with the batch fields worth recording on delivery.