Dealing with sediment

Sediment in an older red is precipitated colour pigment and tannin — compounds that were dissolved in the young wine and have slowly bonded into particles too large to stay in solution. It is the wine, not a contaminant, and it is the visible evidence of the softening that made the wine worth keeping.

It is also gritty and bitter, which is the only reason to remove it.

The other common deposit is entirely different: tartrate crystals, which look like sugar or fine glass and usually cling to the cork or the base. They are potassium bitartrate — cream of tartar — dropped out of solution by cold, and they are found in young wine as often as old.

Neither is a fault, and neither is grounds for returning a bottle. What both do require is a little care in pouring, because the last glass of a bottle is where all of it ends up.