Floating Density Ball Science Demo Equipment Stainless Steel. #64982-00 by Boreal Scientific. This density ball is used to demonstrate the density of a liquid varies with the temperature of the liquid. This apparatus is a 4" stainless steel hallow sphere filled with water and sealed to prevent leakage. Directions are included along with an explanation of the basic theory explaining density variation with temperature. Original box. Condition is "Used". Shipped with USPS Priority Mail.