At one point, the glass makers of Italy found a problem because of unscrupulous dealers.
The process of making delicate dishes consisted of subjecting the substance to a severe heat. Often a piece of china came out of the oven with cracks and could not be sold as perfect. But, many of the dealers used an invisible wax to coat over the cracked surface.
At a casual glance the buyer was not able to distinguish between the good and the bad product. Only by holding the plate up to the sun could the crack be seen. So the honest dealers banded themselves together and devised the use of a stamp to be used on all good pieces. This stamp bore the marks – "sin cera," or "without wax," from which we get our word sincere.
Often, when the patched-up dishes were exposed to the heat the wax would melt and the flaw revealed. The fiery trials very often revel the wax of insincerity.
