King Seven wrote:Tiger mottling is still an interesting one, though I suspect that is down to small particles of roasted coffee suspended in the foam. Except the way it forms sometimes is a bit odd. Should probably get the microscope and camera out!
I've been thinking about it. I'm not sure it's a sign of quality. A slow start/fast finish pour will tend to be dark at the edges and light in the center. This cannot be a brew strength mechanism, since that only applies to the overall color. As the flow gets more even, one gets tiger striping, if the flow is very even, uniform crema.
Since it's unlikely that slow flow will dislodge more solids or oil droplets (which could also appear black due to prism like optical effects), it may be the fines that get through the basket's screen. These would appear early in the shot. If the flow is slow at that point, they don't mix, and get pushed in an orderly fashion to the edge. If the flow is faster, there's some mixing and tiger flecks. Fast flow gives complete mixing and no visible flecks (although they could be there, broken up into smaller patches, visible with a loupe)