The cream of tartar or wine stone is formed as by-product during wine production. It consists mainly of potassium hydrogen tartrate. It is used in the diet, namely as a stabilizer, a pH regulator, an antimicrobial agent, an auxiliary technological and as a thickening agent in various products. Our goal was to determine efficient procedure for the recrystallization of tartar and to obtain the highest yield of pure potassium hydrogen tartrate (»wine diamonds«). Next, we wanted to use recrystallized cream of tartar for preparation of baking agents that are comparable to commercially available baking agents. The composition of “wine diamonds” and the percentage of potassium hydrogen tartrate in the ”wine diamonds” was determined by atomic absorption spectrometry (AAS) and by titration with NaOH. We measured the volume and rate of carbon dioxide release from bakery products composed of different proportions of potassium hydrogen tartrate and sodium hydrogen carbonate compared to two commercial baking agents - Pecin (Gorimpex) and Baking powder with cream of tartar (Gorimpex). Baking agents of different composition were used to bake cakes and performed sensory evaluation. The best quality cakes were prepared by using commercial baking agents and baking agent prepared in our laboratory consisting of potassium hydrogen tartrate and sodium hydrogen carbonate in mass ratio 2:1. We also measured specific volume and colour of crumb and crust of different cakes and breads.