I was looking over the spell list again, looking for new ways to use old spells, or ways to use seldom learned/taken spells. I noticed Reinforce and thought it might be nice to cast that on the result of a Physical Barrier, as the drain code is nicer. The TN for the barrier spell is 6. The TN for the Reinforce spell is Object Resistance.

The lowest given Object Resistance is 3 for Natural items like trees, soil, and water (BBB p.182), and the more processed or technological the thing is the higher the TN goes. A magic barrier seems like it should have an even lower TN than a purely physical item, and knowing a TN must be a minimum of 2, would magical constructs have an Object Resistance of 2? I do not ever recall reading about anything along this line. Actually, this is one of the few instances I can think of casting an OR TNed spell on a magical target.

On the plus side it make physical barrier much more appealing and workable, even when casting with sustaining mod's to TN.
On the minus side my take is that it is perverting the spirit of intent in the spell reinforce slightly.
I would opt for an on object rististance of 3 just to stop munkining being called.
Nice combo, the character after all is taking twice the drain and two actions to get the bonus. So on the whole I think its balanced.
Even if you include sustaining foci.

Leaving out any concerns about munchkinism, what should the Object Resistance of a purely magical construct be?

I think the simplest way to measure it is by the force of the spell creating the construct... I'm sure there could be arguments for more or less than the force, based on the intent and design of the spell and perhaps initiation level of the caster, but for simplicity's sake I'd use the force of the spell, at least as a baseline or guideline.

A purely magical construct is similar to a virgin telesma, after all it is created with mana.
In theory it should be lower than natural objects but I would keep it at 3 just for mechanics. A OR of two leads to the uber shield when you factor in the number of dice a hermetic can bring to bear.

It might be worth trying it the other way, things highly processed or altered with magic have higher ORs as well. Only stuff 'naturally grown' has the basic low TR. Any monkeying around with it after that increases the OR number.

I wouldn't bother trying to find sense or reason in OR, especially given what other things make use of it. Any ruleset that makes it easier to light uncut granite (OR 3) on fire than hydrazine (absolute minimum OR 5, more reasonably 8 with a -1 due to flammability) needs to be discarded and replaced badly.

~J

Yeah... so it would be much easier to light the water then the paper cup thats holding it.
I tend to just have my hands willy nilly at anything needing an OR test, or make it up as I go along.