The first casting from the foundry! The square block at the top is the riser which provides a reservoir of molten metal that is drawn into the casting as it solidifies and shrinks. There seems to be a few slight dents in the cast, likely the wax pattern was dinged before it was put into the investment. They should come out in the polishing, though are couple are pretty deep. Now it is off to for machining.
This leads me to a discussion of the material. This is a functional prototype made from a brass alloy similar to C69400, which is not an ideal material for a couple of reasons. The first is that the lead content likely exceeds allowable levels (0.3% in the US). The second is that C69400 has no additives to prevent (or rather retard) dezincification, the process whereby the zinc is stripped from the metal leaving a weak and brittle copper sponge which can ultimately lead to failure of a part at pressure. Dezincification resistance is especially important for espresso machines because of the operating temperature, the acidity of coffee and often, due to the use of water softeners, the mild salinity of the water itself.
From the excellent copper.org website:
[i]Sand-cast faucets and other plumbing components have traditionally been made from leaded red, semi-red and yellow brasses. The most common plumbing brass, C84400 (also known as 81 Metal or 81-3-7-9) contains nominally 7% lead. The most popular red brass, C83600 (85 Metal, 85-5-5-5), contains nominally 5% lead. Permanent mold and pressure die castings of plumbing components are also commonly made of the leaded yellow brass alloy C85800, which contains nominally 1.5% lead.[/i]
Lead is added to brass to improve machinability. It acts as a lubricant and causes the chips to break into small pieces while it is being cut. Worse still, because of the way the lead crystals form as the liquid metal solidifies in the mold, the concentration of lead is highest at the inside surface - i.e. where it comes into contact with the water. The unfortunate conclusion is that it is highly likely that both my machines (and indeed all vintage espresso machines), help me meet my recommended daily dose of lead in the morning. This was just the way things were was until California passed its law in 2006. Since then, considerable effort has been made to find alternatives to leaded brass.
This leads me to a discussion of the material. This is a functional prototype made from a brass alloy similar to C69400, which is not an ideal material for a couple of reasons. The first is that the lead content likely exceeds allowable levels (0.3% in the US). The second is that C69400 has no additives to prevent (or rather retard) dezincification, the process whereby the zinc is stripped from the metal leaving a weak and brittle copper sponge which can ultimately lead to failure of a part at pressure. Dezincification resistance is especially important for espresso machines because of the operating temperature, the acidity of coffee and often, due to the use of water softeners, the mild salinity of the water itself.
From the excellent copper.org website:
[i]Sand-cast faucets and other plumbing components have traditionally been made from leaded red, semi-red and yellow brasses. The most common plumbing brass, C84400 (also known as 81 Metal or 81-3-7-9) contains nominally 7% lead. The most popular red brass, C83600 (85 Metal, 85-5-5-5), contains nominally 5% lead. Permanent mold and pressure die castings of plumbing components are also commonly made of the leaded yellow brass alloy C85800, which contains nominally 1.5% lead.[/i]
Lead is added to brass to improve machinability. It acts as a lubricant and causes the chips to break into small pieces while it is being cut. Worse still, because of the way the lead crystals form as the liquid metal solidifies in the mold, the concentration of lead is highest at the inside surface - i.e. where it comes into contact with the water. The unfortunate conclusion is that it is highly likely that both my machines (and indeed all vintage espresso machines), help me meet my recommended daily dose of lead in the morning. This was just the way things were was until California passed its law in 2006. Since then, considerable effort has been made to find alternatives to leaded brass.
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