Gallon of Acid
An acid wash is the purposeful stripping of a thin layer of plaster, exposing fresh plaster beneath. Therefore, it is ill advised to make it an annual custom, which will accelerate the need for re-plastering. Most plaster coats (sometimes called whitecoat or marcite) are in excess of 1/2″, so a careful acid wash every 5 years won’t hurt.
You may also decide on an acid wash not because of swamp conditions, but just to bring out a brighter, whiter finish. Mineral stains and/or deposits, chlorine stains, even dirt stains… an acid wash is always a dramatic aesthetic improvement to a plastered pool or fountain.
Picture shown is for illustration purpose only. Actual product may vary.