THE CHEMICAL SOLUTION IS TOO STRONG
If chemicals are used undiluted or diluted with insufficient water, they may leave a residue on the surface. This can make the surface sticky and look streaky and may be too harsh on the surface.
i.e. A sticky surface will attract and hold on to more dirt, an overstrong mopping detergent may soften a floor sealer or a solvent-based detergent could remove paint.
Overuse means waste by using too many chemicals, which costs money and won’t do a better job than chemicals at the right strength.
THE CHEMICAL SOLUTION IS TOO WEAK
If the chemical is diluted with too much water it will result in a weak dilution.
A weak chemical solution will not clean properly, leaving a soil residue on the surface. The surface may look clean, but it will sneak up on you and get dirtier without you realising it.
Soil build-up over time will eventually need heavy-duty cleaning to restore to its original condition. The dirty residue may leave the surface still greasy or slippery which may be a hazard.
As a general rule, if in doubt start weak and gentle, and work up to a strength that gets the job done.