The phrase "a layer of solid" is correct and usable in written English.
It can be used when describing a physical layer that is solid in nature, often in scientific or technical contexts.
Example: "The geological survey revealed a layer of solid rock beneath the surface soil."
Alternatives: "a stratum of solid" or "a sheet of solid".
Van Eecke: "By tweaking and fine-tuning the existing safe harbour system and adding a layer of solid enforcement we could come to a workable solution.
In the laboratory, fungi are commonly propagated on a layer of solid nutrient agar inoculated either with spores or with fragments of mycelium.
This research assessed the feasibility of creating a layer of solid lubricant using the plasma electrolysis method.
It had been pumped dry, but unknown to the operators a layer of solid residue had been left behind in the vessel.
Creating a layer of solid lubricant on the steel surface is one of the measures of protection against harsh conditions to which service parts are commonly subjected.
If this were the only process, the intensity of the hard component passing through a layer of solid material would decrease by the same amount as in an equivalent layer of air.
Imaging and selected-area electron diffraction show that a layer of RuO2 solid forms on the surface of bulk PS specimens exposed to RuO4.
They spread an ultrathin layer of one such liquid, carbon tetrachloride (CCl4) on a cold metal surface and then added a layer of amorphous solid water on top.
The observed friction contrast between a single and a double layer of solid solution suggested a difference in composition between layers.
A layer of accumulated solids, called sludge, forms at the bottom of the tank and is periodically removed.
This latter assay consisted of measuring the 24 h uptake of tritium labelled thymidine into cells plated in liquid medium upon a layer of semi-solid agar.
