Listen to part of a lecture in an art history class.

The professor has been discussing the Italian Renaissance.

In our discussion of Italian Renaissance paintings from the 1400s and early 1500s, we've looked at some masterpieces on canvas and on wood... but our discussion would be grossly incomplete without talking about frescoes.

Frescoes are basically paintings done on the interiors of buildings-on walls and ceilings.

They weren't invented during the Renaissance-if you remember, we looked briefly at fresco paintings way back in our discussion of ancient Romans and ancient Roman art a few weeks ago.

But it was much later, during the Renaissance, that the term "fresco" was commonly used.

It's an Italian word that means, literally, "fresh." And... well... to explain that, we have to get specific about technique.

Back then, most buildings had stone and brick walls with highly irregular surfaces- they weren't smooth.

Also, the walls weren't completely waterproof- moisture could seep in, buildings were often damp.

There was no way to really control humidity inside buildings in those days.

So, because frescoes are done inside buildings, on walls, well, the walls needed to be prepared before work could begin.

So, for example, sometimes thin reed mats were stuck onto the walls... so these thin, reed mats would be- like an additional layer... between the original part of the wall and the frescoes- the painted part of the walls that were done over them.

The reed mats could smooth out the surface of a rough wall, or could also provide that all-important protection from moisture... or do both.

so it was the wall, then the mats, then plaster on top of the mats, then the fresco painted onto the plaster.

Other times, though, plaster was applied directly to the walls- a thick layer of plaster- to fill in spaces between the bricks, to smooth out the wall surface for painting the fresco, you see?

you see?

Plaster is a whitish kind of paste-a mixture of lime, water, and sand....

After you spread plaster on a surface, it'll harden-like cement does.

But as I said, "fresco" means "fresh," and that's because to create a fresco, the paint has to be applied very soon after the plaster's been spread over a surface, right onto the wet, fresh plaster.

By doing this, the painting actually becomes part of the plaster.

Finishing a painting before the plaster dried was a real challenge for fresco painters.

The technique of creating frescoes was developed over time, and eventually perfected during the Renaissance- a time when immense buildings were being erected as symbols of wealth and power... very large buildings which people wanted decorated on the inside as well as the outside.

The owners of these grand buildings wanted to decorate the walls, to reflect their own affluence and prestige.

Now, few people would argue with the greatness of artists from that period- Michelangelo... Raphael...

But there's this popular mental image people have of an artistic genius producing a masterpiece in total solitude.

Well, that idea's fine for canvas painting or other small works... but a practical reality of fresco painting in the Renaissance was collaboration.

The sheer dimensions of the surfaces involved, plus the physical properties of the plaster, meant it was inevitable that Renaissance artists would rely on assistants- apprentices, they were called-to help create their masterpieces.

Artists had to plan the work carefully... divide it into several days.

Each day was a repetition of the same technical process: apprentices mixed paints, prepared the plaster... spread it on one section of the wall or ceiling... then, finally paint on the wet plaster.

This had to be done within a few hours, before the plaster dried.

So, they'd go through that whole process in one day, on one section.

The next day they'd move on and do it again, on an adjacent part.

So, any fresco commissioned to an artist was, for practical reasons, commissioned to a whole team.

Now, I'm not saying a genius like Michelangelo lacked the skill to paint the enormous ceiling of the Sistine Chapel by himself.

But he probably would've had to live until he was 200 years old to finish the ceiling's frescoes like that without anyone's help!

So although we aren't sure exactly how many people took an active role in actually painting the ceiling, we can see areas which are really inferior to Michelangelo's work... that must've been painted by his apprentices.