Those of us old enough to have read Hiscock have heard of varnishing cans etc.

In today's boats, if cans need varnished, there is something wrong with the boat or the owner.'s maintenance.

Even our old home built in 1970 ferrro cement boat did not need varnish on cans. We sold her in England in 1983' three years after crossing. The buyer was impressed by the fact that we still had cans on board stored in the bilge, with US supermarket labels on them, unvarnished and unrusty.