Thought experiment: It's medieval Europe, and you have a bar of lead you want to melt. You are not allowed to have anything that glows hot. How do you do it?
Sit on it, leave it in the sun, breath on it. Lead melts very easilly.
I exaggerate. But lead melts well before the "glow hot" phase, so it is a simple matter.
I respect you and enjoy conversations with you. But I gotta say, that is the weakest argument ever. Medieval knowledge and thought was much more advanced than you give it credit for. They knew that somethings melt at different temperatures than others.
Ignem wards and Intellego spells 
It is a world of magi, you gotta take them into account as well 
Well, so how do you do it then? 
You're allowed any reasonable medieval equipment and materials. Only one rule: you're not allowed to have anything become red-hot. How do you melt the bar of lead? I'm serious here - is this possible without fire?
I'm saying that there was no numerical scale, no units of temperature. Yes, there notional comparative temperatures such as "hot enough to melt lead", "hot enough to melt iron", and so on.
My point is that given that is impossible to measure the melting point of lead, and that it is impossible to accomplish the melting of lead without a red-hot fire, it is by no means clear that the temperature of molten lead is less than the temperature of a red-hot fire. Do you follow me?
Creo Ignem. There, done.
Is it possible without fire OR magic? Sure. I can use an array of mirrors to concentrate sunlight on it. It will get hot enough to burn wood. Just ask Archimedes :mrgreen:
Lenses would do it to, but I am unsure if they can do that yet.
Focussing enough light to spark a flame on wood, yep. Focussing enough light to melt a bar of lead, with medieval mirrors? I'm sceptical... 
It will work. It really will. The melting point of lead is lower that the combustion point of wood. Lead melts at 300f, wood burns at 451f.
Archemedies was well before the middle ages, and he didn't use mirrors. He used highly polished shields. For centuries people doubted the story was true. A few years ago they recreated the story. Bunch of guys holding metal discs (shields), a noonday sun, and a wooden barge with a camera on board. Ship caught on fire. The same could be done with a bar of lead, and I have a hunch it would require substantially less effort. A bar of lead is much-much smaller than a ship.
Ah, but you're not trying to burn the lead. Nor does the wood need to be completely melted - it suffices to heat a tiny spot up to the required temperature, and then the rest heats itself. I might allow that my lead bar has a tiny molten spot on it, which rapidly cools in the open air, but the bar itself endures. Also note that lead is a lot more reflective than wood - less of the light will be absorbed as heat. 
Whatever method the local smith uses?(for example) There isnt a single unified measure, but OTOH, there still isnt.
I did. Go study the history of metalworking.
I melt it with a fire that isnt hot enough to glow, because lead melts long before that. Stupid answer for stupid question.
Yes it is. A sun-oven is plenty enough for lead.
But why should fire be forbidden? If you light a candle, it doesnt get red-hot, but you can still melt lead with it if you´re careful and have a good candle.
EXACTLY!!!
Do you always ignore what people tell you?
That is such a inane comment that you might as well be trying to flamebait.
As has already been said here, NO YOU DONT NEED A RED HOT FIRE TO MELT LEAD FFS!
After you went mad and disregarded reality completely, not really no.
You´re sceptical... Ignorant of such little facts that you can melt iron the same way if you´re very good at setting it up.
And if you go modern, there are some solar power plants using mirrors focusing sunlight on a tiny point, and reaching 5-10 thousand degrees at that point...
Please tell me you´re joking...
Oh for goodness sake, did you skip out on science classes completely in school?
en.wikipedia.org/wiki/Zeroth_law ... modynamics
en.wikipedia.org/wiki/First_law_ ... modynamics
en.wikipedia.org/wiki/Heat_conduction
Adding energy means you add energy, regardless to what material you are adding it. Heat doesnt become something else becasue you´re heating a metal instead of wood.
I think that you are right, it is clearly a mistake.
It seems pretty clear, that the intention is level 5 = "heat something to be hot", level 10 = "heat something to be hotter". The author just appears to have chosen bad examples of "hot" and "hotter".
I don't think it makes much difference, either assume that magic / Mythic Europe is weird or rewrite the examples so that they make more scientific sense.
I'm not sure what the problem is here.
The guideline clearly means "heat an object to 100oC" (forgetting about pressure effects on the boiling temperature). The size of the item depends on the particular target of the spell. It could be an Individual, a Group, a Room, a Structure, etc.
Yes, this is a mistake. It goes back to ArM4, and I honestly can't remember who did the Ignem guidelines for that. Might have been me. Might not.
It took 13 years for anyone to notice it and point it out, and changing the guidelines now would require going through all ArM5 books to check use of them, so that we don't introduce further inconsistencies.
Since, however, it took 13 years for anyone to notice, I am fairly confident that it isn't a critical problem in general. If it is for you, feel free to swap them at home.
However, the Ignem guidelines will not translate into "temperatures created". Igniting wood (4) needs a higher temperature than melting lead (5, if revised). Creating light as bright as direct sunlight on a clear day needs 6,000K to get that spectrum from black body radiation, and that's level 5. Modern science is not true of Mythic Europe, so canon won't let you translated consistently into those terms.
To repeat, there is no numerical scale of temperature, no units of temperature, in the middle ages. A smith could only judge temperature very approximately, not measure it in any meaningful way. Avicenna had a thermometer for measuring the temperature of air, but AFAIK this was not widely known in the west, and could not be applied to measuring the temperatures of fires.
Um, I hate to break it to you, but you do know that the temperature of a candle flame is about 1000 degrees C, right? There is no fire that "isn't hot enough to glow"! Fire is a phenomenon linked to red-hot-plus temperatures, a chemical reaction which requires temperatures that high.
Scream and shout all you want, but there is no such a thing as a sub-red-hot fire. If you're not using red-hot stuff, then you're not using fire, it's as simple as that.
Yeah, that sounds a lot like medieval mirrors...
Is this your idea of debating on the internet? You insult me and then lazily spew out a few Wikipedia links? LOL.
Again, let me spell it out for you:
On the one hand, we have light focussed onto a tiny spot on a piece of wood or paper, which ignites it. On the other hand, we focus the same light onto a bar of lead. Differences:
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Lead has a much higher reflectivity than wood. This means that much less of the light is absorbed and converted into heat. Same light, lower spot temperature.
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Lead is a much better conductor of heat than wood. The absorbed heat gets diffused very rapidly away from the focal point.
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Ignition is a fundamentally different phenomenon to melting. For the wood, you only need to achieve, momentarily, a sufficiently high spot temperature, which triggers the ignition. To melt a large object, you need to apply the temperature over a wider area, over the whole object, for a sustained period.
Bottom line: you can't melt a bar of lead with a magnifying glass, or any non-fantastical/non-modern combination of mirrors or lenses. At best, you will only score its surface.
The CrIg guidelines are not listed according to temperature values, and rightly so, because this makes no sense in medieval Europe. We know that a candle flame has the same temperature as a bonfire, but a medieval person would say otherwise - it's plainly obvious that the bonfire is hotter. The medieval person is not even wrong, because heat is not the same as temperature! For the guidelines one should think in terms of the amount of heat, not level of temperature.
You can certainly (and relatively easily) have selfsustaining fires which are below the temperature at which things glow. They might be tricky to acquire in Mythic Europe though. A bit of lead in a metal pot, however, will melt long before the pot ever gets to read heat. I used to, as a child, play about melting the lead from wine bottles over either a candle or a spirit burner and using it to make molds out of patterns I'd carved into a block of wood.
As far as the mirror-thing goes, the reflectivity of the lead is largely irrelevent. It just descreases the total energy flux into the lead - provided the container is sufficiently insulated the requisite temperature will be reached anyway. If you have something cooling your wood, that would preserve it too. A gentle sprinkling of charcoal onto even white paper will, as any child can tell you, make it much easier to ignite with a lens and sunlight.
Either way, any half-way competent philosopher in ME (and there are a lot of competent ones) can tell you that a fire which has gone out can melt lead, and that molten lead can't melt copper, and so on. Whilst the precise physics of Mythic Europe differ, the observables are largely the same, especially when applied to such fundamental things as metalworking. True, the more esoteric aspects of metalworking may well be magical or alchemical, but the day to day things (like not building a fire next to your lead piping in an old roman villa) are the same.
I would be interested to know what kinds of fires these are.
But what are you using to heat the pot? Fire, presumably...
Theoretically, yes, if you keep adding heat energy to a thermally insulated bar of lead it will eventually melt. In practice, however, heat loss due to radiation and conduction will overwhelm the heating effect of a small source such as that provided by a magnifying glass. You need a bigger source of heat.
Doubt it - wood's a good thermal insulator. You can take a box of matches out of the freezer and they work fine. (OK, I haven't actually tried this, but I'm making an educated guess that this is true!)
Indeed; this illustrates exactly the importance of reflectivity. It would be easier to melt lead if you painted it black, although probably the paint would just burn off.
True, but it's not going to melt a lot. Toss a bar of lead onto some dying embers, and it might temporarily melt at the edges, before freezing again as the fire cools.
I'm not trying to argue that the melting point of lead isn't lower than red-hot temperatures, mind you; what I'm saying is that to achieve a meaningful amount of molten lead in medieval Europe, you will generally need a fairly large amount of heat provided by a fire, and that typical fires glow red- (or white-) hot.
Jeez... Once Direwolf pointed it out the error is as plain and simple as you ever get. Have you some religous attachment to the Ars Magica guildlines?
I always assumed the lower level effect lost efficiency in creating some light and some heat. And being that it is lower level doesn't acually create the heat to make something red hot, but instead makes the thing hot and creates the glow at the same time.
Where the higher level effect creates only heat, but only enough heat to melt lead.
Otherwise lvl 5 + 3 magnitudes for voice is a lvl 20 effect for instant death.
You are forgetting that Ignem is not just heat... it's Fire. Fire is not just light and heat. A lower level effect will not be as controlled as a higher, so it is easer to create a fire, than channeling one aspect of Fire without creating the Fire.
One thing you are overlooking. The Line Editor admited it is an error that traces back to fourth edition. So, that pretty much settles it in my mind 
Lead is dull. It's not actually very reflective. Polished wood is, in my experience, better. Nevertheless, solar ovens exist which are used to melt steel. Whilst they do require large arrays of mirrors, they'd actually be easier to construct in mythic europe than real life since ReTe would make aligning and rotating the mirrors trivial. Your argument seems to be based on scale. By that logic, a very small fire couldn't burn anything or melt anything, and that's not the issue at hand. We're not talking about a small 1-inch mangifying glass here, but multiple, large and focussed mirrors (per the original greek experiment), and that's a lot more energy being pumped into the system. If you can burn wood you can melt lead - it'll just take four times longer due to heat capacity differences.
As far as the matches in the freezer goes, the analogy is false. Firstly, because the ignition in that sense is not by solar power (whose intensity and heating ability is at issue) , nor is there cooling continuous during ignition unless inside the freezer where the sun can't reach it, nor is the cooling particularly efficient even if striking the matches inside the freezer. That, and they'd get wet due to condensation and be ruined. ::grins::
And all of that is basicly unimportant - lead melts before things get red hot. The ancients, who did a great more leadworking than we do today, would know this. Since their knowledge and erroneous assumptions are what Ars Magica's universe is based on, that's what matters. Defending a chance mistake, admitted to be such, on the grounds that it's more mythic when it isn't seems rather pointless.