Density, for example.
To convince yourself of the relevance to e.g. combat, try to find a wooden stick and a similarly sized Iron rod (density similar to that of bronze). Then ask a friend to smack you from behind twice, once with the stick and once with the rod, without telling you which is which. I guarantee you'll be able to tell the difference.
Combustibility is another example.
Bronze does not catch fire. Rope does (unless wet).
I could go on.
Not that I am aware of. In general, one should look at the example effects, particularly from the corebook, to get a sense of what's reasonable. Keep in mind that Terram is specifically the Form you can use to affect "generic solid objects" and/or the "solidity" of objects, possibly with one or more casting requisites (see ArM5 p.79, the Elemental Arts, and ArM5 p.152, Terram Spells).
True... but the spell description is lacking in this aspect which can mean two things.
A- The folks who think that if it isn't there, then the effect is meant to be utilitarian only. A bit like the benefits I listed for the bronze staff/rope
or
B- The spell is poorly described and troupe needs to scramble to figure-out the exact in game effects which as this thread has shown, will vary widely
I would prefer if the spell carried that information such as "...this Bronze Staff, while very pretty, cannot be used as a weapon because it will fall apart..." or "... this Bronze staff is not only pretty, use the stats of the war hammer if used in combat..."
For whatever it's worth, note that both Rope of Bronze and Supple Iron and Rigid Rope have both been around, at the same level and similar description, since at least Second Edition. Stuff was not as well-balanced back then, but perhaps more importantly, it was not so mechanically codified and it was meant to be eyeballed by the Storyguide. In this sense, Ars Magica was quite the precursor to many more freeform systems of today (I once happened to read an enlightening interview in this sense by, I seem to recall, Lisa Stevens).
Also, if you want to have an easy out just consider that many of the spells written down are the more popular ones - and some of them might be popular because they are somewhat more powerful than they should be due to experimentation or other factors.
I typically do... there are some in there that really are more powerful but in the case before us, it ain't so much about being more powerful. It's more about lacking description which has led folks on this forum thinking it could grant anything from -0 to -9 in penalty to attacks.
I actually recall someone using this spell this way in one of my games about a decade ago (so much for long overlooked) and I simply told them they had to choose between pants of shirt as to what they were casting it on. They decided to go with a different spell, but I was prepared to have it completely paralyze the clothing, though not make it any tougher, so it could still be torn to get out of it.
Well, you are the 1st to have someone almost use an alternate version of the effect where it would be 100% effective at stopping legs or arms from moving ("Complete paralyse") which is arguably better than the most liberal interpretation of -9 penalty suggested thus far... and yet, your player still decided on a different spell. Since this close encounter that happened a decade ago, it continues to be overlooked.
We're talking about a Base 1 spell paralyzing a target. In ReCo it is a B5 and is probably selected more often by PC's than Supple Iron and Rigid Rope.
I've used it to tie a rope around things to effectively lock it onto them, allowing for doing things like locking something closed. You could use it like handcuffs similarly. I also use it for rope to keep the rope from getting tangled.
