You have to pour a lot more water into the bucket to compensate for the water that leaks away. The higher the heat conductivity of the material the bigger the size of the holes and the more water you need to be poured into the bucket to fill it. These effects are best observed in the animated version of Figure 3.1 - click on image to see animation. The absorption of the long laser pulse leads to melting and then sputter evaporation of the material which can contaminate the surrounding area, produce microcracks, and remove material over dimensions much larger than the spot. The animation file is 229k in size.
Material is removed by depositing a lot of energy into the melted material which boils.
As shown in Figure 3.1, this boiling ejects globs of the molten material away from the work zone. The ejected globs form drops that fall back onto the surface and contaminate the sample. These droplets can be rather large. They retain a fair amount of residual heat and may bind strongly to the sample. Removal of these contaminants may be difficult or impossible without damaging the target.