Though Bronze has remained relatively unchanged since the alloy combining copper and tin was first discovered, a sculpture’s quality remains very hooked in to how well it's cast. Various defects, like gas porosity–the formation of bubbles within the cooled casting–or cold-front–the imperfect fusion of two fronts of liquid metal–can affect the alloy’s strength, appearance, and sturdiness . Important things to notice when determining the standard of a bronze sculpture include the exactness of the casting to the artist’s model, particularly its surface texture quality and therefore the accuracy of subtle details like fingers. The patina which develops naturally on the surface of the sculpture can show the standard of the alloy used. The colour of the patina can vary from reddish to warm brown, green, or maybe yellow counting on the quantity of copper within the alloy. No matter its color or whether it's present or has been induced with chemical substances, the patina should be even and richly hued. Particularly thick or dark patinas are often won't to hide flaws in lower-quality casting.