The phrase "a darker staining" is correct and usable in written English.
It can be used when describing a color or intensity of a stain, often in contexts related to art, biology, or materials.
Example: "The experiment revealed a darker staining of the tissue samples, indicating a higher concentration of the dye."
Alternatives: "a deeper stain" or "a more intense staining".
The number of colonies caused by RAS was similar to that of AP4 or MYC, but RAS-induced colonies displayed in increased cellular density as evidenced by a darker staining.
In both species it has a darker staining thin edge, possibly corresponding to the waxy layer of the cuticle and a more lightly stained thick internal part likely representing cell wall material.
The result was that GVR-infiltrated areas showed a darker staining than the surrounding non-infiltrated tissue, indicating high levels of starch accumulation.
The wooden steps of the main staircase have a darker stained edge for those with low vision.
Treatment with pronase resulted in a darker stained glycocalyx, which was clearly separated from the plasmalemma (arrows, Figure 4 C).
In one of the muscle fibers stained with mPR130/B α1 AB, we could even observe a darker stained band positioned in the centre of the A-band.
There was little or no decoration, though the joinery was sometimes given a darker stain to emphasize the expert construction.
Letting the stain stay on the wood for more time will create a darker stain.
You can replace the tea with brewed coffee for a darker stain.
"The initial symptom is a dark staining pattern on the leaves," explained Carrie Ewing, a PhD student from Ohio State University.
Fig. 2 Microsporidial spores staining dark violet against a pale-green background in a conjunctival swab specimen from case 3. Microsporidial spores (large arrow) are seen as well-defined oval reddish bodies with a dark staining of the narrow end of the spore (black) or a waistband (white) closer to the tip of narrow end.
