Bird droppings
Acidic, alkaline in places, and gritty. On vehicle paint in sun it etches within hours, and what remains after washing is a mark in the finish rather than on it.
In detail
Bird droppings combine three properties that each attack a finish differently. They are chemically aggressive — a mixture of uric acid and, from the digestive tract, alkaline components — so they attack from both ends of the pH scale depending on the deposit. They contain grit, since many birds ingest fine stone, so any attempt to wipe them dry drags abrasive across the surface. And they dry hard and adhere tenaciously. On vehicle clear coat the combination is worst, because heat accelerates the chemistry and a deposit left in sun etches into the film within hours: the deposit washes off and a dished ring remains, which is a polishing problem rather than a cleaning one. The mechanism generalises to every soft or coated surface — limestone and sandstone are attacked chemically, painted timber and powder coating are marked, and glass is the one common surface that is genuinely indifferent. The method follows from the three properties: soften and flood rather than wipe, so the grit floats away rather than being dragged, then wash normally. Speed matters more than product.
Why
- Bird droppings is explained by Why old stains are harder
- Bird droppings is explained by Coating thickness
Sources for this page
Sources
Glass Technical Paper FB01-00: Proper Procedures for Cleaning Architectural Glass Products
National Glass Association (NGA) with the International Window Cleaning Association (IWCA), 2023 · Trade or professional body
Relied on for: That scratching is caused by abrasive particles trapped between the surface and the tool, and that sufficient water helps prevent it. (cleaninghq's interpretation of what it says)
Verification: a person has read the passage relied on.
Read on — 'Routine Cleaning & Maintenance', including the pure-water method paragraph. Supports the claim as stated.
AAMA 609 & 610-02: Cleaning and Maintenance Guide for Architecturally Finished Aluminum
American Architectural Manufacturers Association (AAMA), 2002 · Standards body
Relied on for: That chemical reactions on a hot sun-heated finish are accelerated and non-uniform and can mark it beyond restoring. (cleaninghq's interpretation of what it says)
Verification: a person has read the passage relied on.
Read on — Read in full. Sections 3 General, 4.1 light surface soil, 4.3 organic coatings, and 5 Cleaning Precautions. Supports the claim as stated.
Care & Cleaning of Natural Stone
Natural Stone Institute · Trade or professional body
Relied on for: That calcareous stone is sensitive to acidic solutions which may dull or etch it. (states this directly)
Verification: a person has read the passage relied on.
Read on — Sprint 29 read all nine sections. Earlier sprints had read three: the siliceous-versus-calcareous classification, cleaning products, and sealing. Supports a wider statement — our claim was widened. Three sections of nine had been read and the source treated as complete. The unread six carry the whole preventive programme - coasters, trivets, non-treated dry mopping, slip-resistant mats, worn vacuum wheels, blot-don't-wipe - none of which the register held. They also answer a priority-1 row reading 'no route answers this yet': the authority's position on etch marks is that they are not a cleaning problem and need professional re-polishing. Two oddities are worth the record: dry 0000 steel wool is permitted on water rings, and efflorescence is removed dry because water makes it worse.
Last reviewed by a person on .