A scraper is provided to keep the disk clean and prevent sticking.
The rectangular scraper (42) began in S.D.
The salt is collected from the surface by means of a sort of wooden scoop or scraper, but in spite of every precaution some of the soil on which it is produced is inevitably taken up with it, communicating a red or grey tint.
The typical implements are flint points or spear-heads, left smooth and flat on one side, as struck from the cave, pointed and edged from the other side; a scraper treated in the same way, but with edge rather upon the side than at the end, as in the succeeding Solutrian and Madelenian epochs.
Owing to the fact that at temperatures between its melting and boiling point zinc has a strong affinity for iron, it is often contaminated by the scraper while being drawn from the condenser, as is shown by the fact that the scraper wears away rapidly.