Halachos of the Daf - Bava Basra 89

Accurate Weights

It is a Torah prohibition to weigh something with an inaccurate measure, weight or scale. Furthermore, one may not keep such items in his home. However if everyone in his community uses scales weights or measures which are engraved with a certain symbol, then he may keep the inaccurate ones in his home. This is because no one will buy from him if he uses those weights.

One may not store his weights in salt. Some Rishonim understand the reason to be, because the salt would make the weights heavier, and the buyer might use these weights to his advantage. Since if for example the weight weighs a pound, and after it was kept in salt it weighs a little more, the buyer stands to gain more merchandise for his money. Other Rishonim explain that the reason weights may not be stored in salt is because the weights will decrease in volume, and the seller might use it to his advantage.

One should cover the weights which are used to weigh gold and silver, for even the slightest nick can cause a large discrepancy in price.

A scale must be perfectly balanced. The proper size of the scale is essential to achieve accurate results.