What a micron count measures
A film thickness, in micrometres, measured across the sheet. It is a real dimension, and within one maker’s range it ranks products correctly: a 500-micron cover has more material in it than a 200-micron one and behaves accordingly under handling.
It also fixes a rough price ladder. Micron count is the main driver of what a given size of cover costs.
Why it predicts survival and not warmth
It does not promise a temperature. A stated “up to 8 °C” gain is a manufacturer’s claim about conditions the manufacturer chose, and it is reported here as such — with the conditions where they were given and with a note where they were not.
It does not promise a lifetime. Ultraviolet exposure, how a cover is stored off the water and whether it is dragged or floated on and off do more to its survival than a hundred microns.
And it does not promise it will fit. A cover is cut oversize to the pool and trimmed, or bought to a published size, and neither is settled by the thickness.
The figures that finish the description
Bubble diameter, in millimetres, which changes stiffness and conformity. Size against pool size, because a cover that reaches the water’s edge and no further cannot be handled. Cuttability, which the maker states or does not. And colour, printed as a fact with any behaviour attributed to it kept separate.
On the other cover families the same idea appears in other units: a winter cover publishes fabric weight in grams per square metre or a denier count with a coating, and a ground cloth publishes a thickness in millimetres.
Solar covers, and the other three cover shelves
Solar covers, where microns are the headline. Winter covers and summer pool covers, where the equivalent figure is areal weight and where the useful companions are eyelet spacing and drainage rather than bubble size. And ground cloths, which publish thickness for a sheet whose job is to stop a stone reaching a liner.
What readers keep writing in to ask
Does a thicker cover heat more?
Marginally and indirectly. Most of the gain comes from stopping evaporation, which a thin film does nearly as well as a thick one. What thickness buys is durability — resistance to being dragged, folded and left in the sun. Where a maker publishes a heat-gain figure, the page prints it as the maker’s claim.
What does bubble size change?
Larger bubbles hold more air per unit area and are stiffer; smaller ones conform better around a step or a corner and are usually easier to cut. Makers publish the diameter in millimetres, and it is a genuine difference in use rather than a styling detail.
Can a solar cover be cut to shape?
Most can, and makers say so — it is one of the few properties of this shelf that is reliably published. Cutting normally means trimming the film to the pool outline and leaving the bubbles intact; the page reports what each maker states rather than generalising.
Why do some covers list a colour?
Because the trade attributes different behaviour to blue, clear and dark films. The published figure is the colour; the behaviour attributed to it is a claim, and this site reports the claim as a claim and the colour as a fact.
Last reviewed 21 September 2026