Potassium hydroxide

What not to do

In detail

Potassium hydroxide is sodium hydroxide's twin, and domestic products are formulated on whichever is cheaper or more soluble for the job. The New Jersey fact sheet does something its sodium counterpart does not — it says how much is in the bottle: liquid drain cleaners contain 25 to 36 per cent potassium hydroxide. That figure is worth having, because it turns a category statement about caustics into something a reader can weigh against what the same sheet says happens on contact, which is that this is a highly corrosive chemical whose contact can severely irritate and burn skin and eyes leading to eye damage. On surfaces the decisive fact is a metals one. Potassium hydroxide is corrosive in moist air to aluminium, zinc, tin and lead, forming flammable and explosive hydrogen gas as it goes. Aluminium is the one that matters domestically, because it turns up as bakeware, pan bases, extractor trim and window frames, and a caustic oven or drain product that touches any of them does visible, permanent damage. It also attacks some plastics, rubbers and coatings, and reacts violently with strong acids.

What works

• Potassium hydroxide is effective against Grease Supported

  It converts fat into soap rather than lifting it, which is why it works where a detergent has already failed.

Why

• Potassium hydroxide is explained by pH in cleaning
• Potassium hydroxide is explained by Saponification
• Potassium hydroxide is explained by Alkali attack on light metals