I was always under the impression as a kid that those big tall pillars typical of Roman buildings were always solid marble. I have always wondered how they got so smooth and so shiny.
I also learned as I grew up that a lot of the time, structures (such as bath houses etc) were created out of brick and then ‘wrapped’ or ‘clad’ in marble.
What I want to know is;
How did Roman’s make pillars out of SOLID marble and make them so smooth?
How did Roman’s use marble as a cladding material? How did it stick to walls etc? Nails?
Are these ^ skills we’ve lost over time, or can it still be done to the same degree of intricacy and still look good/ornate?
I saw green/red looking marble, which I believe is jade/jasper - this was used to clad things too. Was the process for doing so the same as marble?
This stems from a recent trip to Rome. The Caracalla Baths (?) were once entirely clad in marble. But now, only a brick shell remains.
I'm sure a dedicated expert on Roman building will arrive to give you a fuller answer, so here's a short one to keep you going in the meantime.
Roman building was characterised by use of marble over travertine (limestone) for stone dressing and cladding - Caesar Augustus legendarily said " “I found Rome a city of bricks and left it a city of marble".
However, marble isn't a great construction material on its own as it can have hidden cracks and fissures that would be likely to collapse under the great weight of an all-marble building. Certain types are also particularly prone to damage from freezing, particularly when cut/shaped in ways that allow water to permeate into previously-sealed fissures.
The secret to exploiting marble as a building material is lime mortar - a mortar which bonds with calciferous stones like limestone (think of most stone-built European churches) and marble. Rather than sticking to the surface a chemical reaction makes the mortar become part of the stone and vice-versa. A well-mixed lime mortar in a limestone wall is many times stronger than modern Portland mortar between bricks.
The Romans built for the appearance of weight and solidity while exploiting clever techniques to keep the weight low but the integrity high. Their expertise was largely inherited from Hellenistic building practice but it seems that the Romans were set apart by their development of technical expertise with limes and concretes. They perfected the technique of "mouldable" marbles using marble dust (a calciferous rock) in lime mortars, which allowed them to create panels that could be plastered on to other surfaces such as flat walls and pillar cores. Different marble dusts could be used to mimic different types of marble.
Another technique for marble columns was to dress (carve/smooth) marble for the outsides and fill the cores with mortar and hardcore (loose, broken stones). Again, the calciferous properties of marble ensured a strong bond with lime mortars in the same way that dressed limestone does in church columns. Whatever the technique that was being used the finished result could be polished with water and fine marble dusts to create an incredibly glossy sheen.
^(Sources:)
^(Roman Building Materials, Construction Methods, and Architecture: The Identity of an Empire; Strickland M; 2010 ()^(Link - well worth reading!)^())
^(Roman Building: Materials and Techniques; Adam J; 2005)
I'm not an expert on Roman architecture, my expertise is more Roman cultural history, but I did spend 2 months in Rome studying under archaeologists with decades of expertise in this last year.
They literally cut them out of the ground at full size - so if you want an 80 foot high column, you literally just cut that out in a big block. Most white marbles, such as Proconnesian, came from enormous quarries in Greece/Thrace/Asia Minor and then were worked into the right shape. Then you'd have lots of workers gradually filing/sanding the marble into the rounded shape. At the abandoned Roman city of Ostia you can see a lot of half finished columns, as most were only completed after shipping, due to the risk of them breaking during the voyage or the ship being lost at sea. There's tons of incomplete/broken columns in their original quarries which show the various stages of working.
They worked it into thin panels. These were then attached to the brick walls via iron clamps. If you saw the weird square holes in all the bricks at the Baths of Caracalla (and most other Roman structures), those are where the clamps were. In late antiquity and beyond most of these were then stolen due to iron being so valuable.
I couldn't comment too much on this but many renaissance and early modern sculptors of marble achieved mastery in their craft. The reason we don't see marble clad buildings to the same extent today is just the sheer cost involved. You'd need hundreds of workers over the various stages of the process, who would need paying a fair wage. In antiquity slaves provided most of this labour. Additionally there are less marble quarries today than there were in antiquity, which increases the cost further.
Green/red porphyry was in essence the same when used as cladding. However the rarity and toughness of this stone meant it was incredibly expensive and thus it was only used for cladding rarely. I've seen examples first-hand at the Villa of the Quintilii just outside Rome, but not many other places. It was more likely to be used in flooring, and you can see this in many of Rome's medieval/renaissance church floors, where Roman marble floors were taken and completely reused. You also see columns of green/red porphyry such as at the Basilica of Maxentius or the Temple of Romulus in the Roman Forum, but they are generally much smaller than white/grey marble columns. Red porphyry statues are gorgeous as well!
Again this isn't really my area of expertise, and I'm sure someone will give a much more detailed answer, but I hope this gave some insight. I spent way too long learning about all the marbles whilst in Rome so it's nice to have the chance to use that knowledge a little!