Exterior bronze sculptures benefit from cleaning with a soft cloth and rewaxing periodically.
Glass aggregate sculptures benefit from cleaning and re sealing every few years as well.
Glass mosaic sculptures sited outside will benefit from on average 1 day every 2 -10 years maintenance by the artist or trained professional at cost of £200 per day plus any travel. Charge will increase in line with inflation only. Maintenance entails cleaning and any touching up or regrouting necessary.
The location of the sculpture greatly effects the amount of maintenance required: a sheltered spot will mean very little or no attention is required and an exposed site will require more.