DELFT CLAY: By far the most well known sand (called clay due to how compact it gets) on the market and the favorite by many due to it's ability to hold it's form when removing objects that have been pressed into it. Super for detail but also very dense which I find can be a negative when working with fragile objects that may crush since the sand grain is so fine and compacts so hard. It has no give. Delft is also the most expensive of the other sand options but since oil based sands have a long shelf life this isn't too big of a deal. I only sell Delft Clay with a kit and not alone due to it's high cost. ***This sand also requires venting to remove air and gas build up when molten metal is poured. ***Good ventilation is a must!
PETROBOND: Very similar to Delft but a more course grain which makes it not compact as tightly and can break apart if a person isn't extra careful when removing an object. In detail tests between both Petrobond and Delft I haven't noticed a big difference overall but Delft is just easier to remove the objects. It is however, much easier to press or compact fragile objects into so in some ways I think it may be a great idea to have both if sand casting is a big part of a business. ***I also feel that Petrobond is best for the beginner since it requires no venting and is quite affordable. ***Good ventilation is a must!
ULTRA RED FINE: This is my brand of sand which I mix with what is known as a Sand Muller. My sand is kind of in the middle of the two being fairly decent at object removal yet fluffy enough that it doesn't harm fragile objects as easily. It is however, a big pain to mix plus not so easy to get all ingredients making it not always available, something I hope to solve in the years to come. ***It really doesn't require venting but I do it anyway if a piece took extra time to prepare. ***Good ventilation is a must!