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High Spots / Low Spots
Quick answer: High spots are patches of ceramic coating left too thick because they were not levelled in time; low spots are areas that received too little or no coating. High spots look smudged or rainbowy; low spots often show weak hydrophobics.
What it means
During application the film must be levelled within the open window. If excess product remains, it cures proud of the surface as a visible high spot. If a section is missed or wiped too aggressively, it becomes a low spot with little or no protection. Both are application defects, not product failures.
Why it matters
Too much product and too little both leave evidence. High spots show as dull smudges, streaks or iridescent patches that will not buff away once they have cured, while low spots do their damage invisibly by reducing durability and leaving water behaving inconsistently across a panel.
Correction differs for each. A cured high spot generally needs machine polishing to remove, and a low spot usually means going back and reapplying locally, so neither is a wipe-over fix once the coating has set.
The cost is not only in labour. A coating that looks patchy or feels uneven panel to panel undermines confidence in the whole job, and a customer who has just paid for protection notices inconsistency faster than almost anything else.
Where each one shows up
Coating instructions, quality control checks under raking light, and post-delivery inspections when customers notice patchy water behaviour after the first wash.
Context
High spots and low spots are the two ways an uneven application shows itself, and both trace back to the same cause: product left too long or spread too thin during the levelling window. They belong with flash time and cure time in the group of terms about timing rather than chemistry.
Common mistakes
- Trying to wipe away a cured high spot with quick detailer - it needs polishing once fully set.
- Overloading the applicator or working areas that are too large for the conditions.
- Levelling without proper lighting, so overlaps and edges are missed.
- Assuming patchy beading means the coating has failed everywhere - it often indicates local low spots.