1. Dissolve 250ml washingsoda in 500ml boiling water. Add 500ml quikcklime. The mixture should form a thin paste. Warning: quicklime reacts vigorously when mixed with water and can cause injury.
2. Apply two thin coats of the cold mixture to the surface to be stripped.
3. Leave for 24 hours and then scrub off and hose down with water.
4. Neutralise the surface with equal parts vinegar and water.

Source: 1 000+ Hints for the Home by Solet Scheeres (Human & Rousseau)