Bad vacuum

Change oil in vacuum pump. Pump should be serviced on a regular basis.
Check for leaks in vacuum pipes and chambers.
Check mixing and pouring chamber are pulling equal vacuum levels.

Dust on waxes or trees

Ensure once waxes or wax trees are made, they are stored in a dry, clean and dust-free atmosphere. Do NOT store waxes or trees in the same room that you weigh powder or invest in.

Rough waxes

Ensure excessive talc or release agent is not used, as this will produce rough waxes and therefore rough castings.

Under or over worked

Follow the recommended mixing instructions.

Not vacuuming flasks after pouring

Ensure flasks are vacuumed for 1 minute after being poured.