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D&D 5E Question on prestidigitation cooling and heating matter

Utility cantrips, and Prestidigitation, especially, typically do many and varied things. When you gain in breadth, you lose in direct power. We may disagree on exactly how much direct power one should lose.
this is why I love the utility at wills (not just cantrips) a big part of my sorcerer/warlock was collecting as many at wills as I could (but only toll the dead as combat) then useing invocations for speak with animals and speak with dead at will
 

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So, every 6 seconds you can warm or chill a cubic foot of material. That's 10 cubic foot per minute and 600 cubic foot per hour. That is 17 m3 of material. If that's water, that is 17 tons per hour (4.7 kg/s).

Assume you can heat that by 10 degrees Celsius. Using the specific heat of water of (about) 4200 J/kgK, the power is 4.7*4200*10 = 197 kW.

That is the equivalent of 100 kettles that you may have in your kitchen. Note that this assumed you heat it by a mere 10 degrees Celsius. If that's 20 degrees, it doubles. That's pretty spectacular from an engineering/physics point of view.

So, the key question here is: how much power (literally heating power) does a cantrip have? I'd rule that this can only be used for flavoring, and not for solving actual quests, challenges or puzzles. Also, I would put restrictions on the heating; i.e. you cannot heat the same cubic foot more than once per day (to avoid abuse).
 

TheSword

Legend
As a long term DM, if a player told me they wanted to have prestidigitation cool down their armour in the desert, I’d allow them advantage on the saves, just like I wouldn’t of someone came up with a technological solution to the problem. They have applied reason to solve a problem… winner.
 

Umbran

Mod Squad
Staff member
Supporter
That is the equivalent of 100 kettles that you may have in your kitchen. Note that this assumed you heat it by a mere 10 degrees Celsius. If that's 20 degrees, it doubles. That's pretty spectacular from an engineering/physics point of view.

There's lots of things that indicate that normal thermodynamics need not apply in your typical D&D world, but yeah.

i.e. you cannot heat the same cubic foot more than once per day (to avoid abuse).

I imagine that this will inevitably start Ship of Theseus arguments as to what constitutes "the same" cubic foot. If I remove and replace one cup of water, is it the same? If I remove and replace half of it, is it the same? If I have a 10 cubic foot reservoir, and I am cycling it one cubic foot at the time, how many cycles before it stops working? Or is the "same cubic foot" a function of location on the map grid, so that if I move four inches to one side, it isn't the same cubic foot anymore?
 

Ancalagon

Dusty Dragon
So, every 6 seconds you can warm or chill a cubic foot of material. That's 10 cubic foot per minute and 600 cubic foot per hour. That is 17 m3 of material. If that's water, that is 17 tons per hour (4.7 kg/s).

Assume you can heat that by 10 degrees Celsius. Using the specific heat of water of (about) 4200 J/kgK, the power is 4.7*4200*10 = 197 kW.

That is the equivalent of 100 kettles that you may have in your kitchen. Note that this assumed you heat it by a mere 10 degrees Celsius. If that's 20 degrees, it doubles. That's pretty spectacular from an engineering/physics point of view.

So, the key question here is: how much power (literally heating power) does a cantrip have? I'd rule that this can only be used for flavoring, and not for solving actual quests, challenges or puzzles. Also, I would put restrictions on the heating; i.e. you cannot heat the same cubic foot more than once per day (to avoid abuse).
A way to limit this (somewhat) is the consideration that cantrips may be somewhat strenuous. Can someone shoot a longbow arrow every 6 seconds? Sure. Can you do that for an hour? I don't think so. Same with a cantrip, after a few minutes of constant casting you might start having significant mental fatigue

I also checked your math and yeah, even if you can only sustain it for a few minutes, that IS indeed 197 kw of power - that's over 250 horsepower.

I suppose at this point we have to ask ourselves, is this reasonable for a cantrip? Maybe water is notoriously hard to heat/cool with a cantrip. I can see a wizard asking his apprentice to boil water with magic , and after impassively watching them struggle and exhaust themselves for a bit, tell them "this is how you do it" and they light a fire with cantrip so that fire can boil the water...

lastly, I'll note that while these calculations are fun, they can be... frustrating at times. I remember one player who wanted to use a fireball to evaporate an amount of water of the same radius as the fireball. If my math is right, that is about the same amount of energy as 0.5 kiloton of TNT....
 


Stormonu

Legend
My ruling as a DM;

Prestidigitation affects a cubic foot. If you can fold your cloak in that 1-foot cube, it will be warm. I'd think of it like a small-volume dryer...
I think significant bonuses to environmental effects is beyond the scope of this cantrip, but I could see that magically out-of-the-dryer warm clothes could count as proper winter/desert clothes in this context (i.e. saving you from the penalties when inappropriately dressed)
I agree with this interpretation.

The effect was originally one of the many cantrips from 1E's Unearthed Arcana. Perhaps the text will help?

ChiI I (Evocation)
Area of Effect: 1‘ cube
A cantrip of this nature allows the caster to cause non-living liquid or solid material to become about 40° F. cooler than it was, subject to a minimum temperature of freezing. The chilling effect lasts for but an instant, after which the subject warms slowly back to normal temperature. Verbal component is a soft whistling, somatic is a downward thrust thumb.

Warm (Evocation)
Area of Effect: 1' cube
This cantrip is the same as chill, except that the magic brings a warming of the liquid or solid. The temperature will rise at most about 40° F.
The cantrip will never cause living creatures to become warmer than their normal body temperature. Components are an aah sound vocalized while the hands are rubbed briskly together.
 

Blue

Ravenous Bugblatter Beast of Traal
I thought about my response, and then double-checked my assumptions about how I've let it been used in the past, and found I had a double standard.

I've had no problems with cleaning or drying a set of clothes, without having to remove them first. So I have established precedent that the object just needs to be a cubic foot of material or less.

I would allow it to ease non-mechanical aspects, and since I'm a DM who likes players to think of clever solution, I could give it a bonus against non-damage other effects.
 

TheDelphian

Explorer
I think the spell limits things to three effects at a time so no more than three cubic feet could be heated or cooled at once. It magically starts and magically stops.

Also it couldn't, in my mind, heat or cool enough to inflict any sort of damage so no boiling water or frozen water as either could be damaging. it is not the intent/power level of the cantrip.
 

Celebrim

Legend
Prestidigitation has an interesting history. Originally, when cantrips were introduced in 1e, the were spells that had the defining feature they couldn't do anything of consequence. They weren't allowed to do anything meaningful. They were essentially spells that were 99% color, or at least were intended to be 99% color.

When the 3e writers looked at the concept of cantrips, they wanted to use cantrips as a means of giving low level spellcasters more meaningful things to do and so created cantrips that could do minor meaningful things. All the meaningless things that cantrips could do in 1e were bundled together in a single spell, Prestidigitation that let the caster do as many meaningless things as they wanted for an hour or so. But again, while these things were intended to be meaningless, sometimes they are actually meaningful and mostly those cases are annoying. So what Prestidigitation could do was left up to "Rulings not Rules" even in 3e, with the expectation that the DM would be able to manage questions like this when they came up.

Of course, that's just setting the stage for table arguments and headaches.

I can't really answer the question for 5e, but I did try to address this question explicitly in my rewrite of the 3e version of the spell which you may find helpful.

Here that is:
Prestidigitation
Universal
Level:
Brd 0, Sha 0, Sor/Wiz 0
Components: V, S
Casting Time: 1 standard action
Range: 10 ft.
Target, Effect, or Area: See text
Duration: 1 hour
Saving Throw: See text
Spell Resistance: No
Prestidigitation is actually a collection of very simple and basic spells, which can be cast repeatedly, quickly and without strain, and used in combination by a creative magician to create an almost endless variety of effects.

Although you cannot use prestidigitation to change an item’s actual properties, you can use prestidigitation to slightly alter how something appears and is perceived. You can alter the color, taste, odor, and feel of an object as long as it remains in range. These changes are superficial and obvious to a trained eye, but can fool casual inspection or less keen observers. The effect of this is to give up to a -5 penalty on attempts on skill checks to appraise, detect or analyze an object, depending on the suitability of the change. For example, making a bit of clear glass appear to be a diamond, or making a bit of bad wine taste like good wine are very suitable changes.

Prestidigitation can be used to move items weighing up to a pound slowly, at the rate of 5’ per round. Light weight ropes can be ordered to knot or unknot themselves, allowing certain use rope checks to be made at a distance. It can also be used in this way to move dust or dirt off or on to objects or separate and sweep light objects into piles. Items occupying up to 1 cubic foot can be cleaned, soiled, or gathered in this way per round. Alternately, very light weight objects such as raindrops can be held at bay, as an umbrella of force. This screen is however insufficient to seriously impede actual missiles or even hurled stones. Prestidigitation can be used to move the air and create slight drafts or breezes similar to that created by a hand fan. It may also be used to slightly chill or warm a small object, but never enough to create pain or injury. By creating cooling or warming breezes and other minor alteration of the environment the spell caster may grant up to a +2 circumstance bonus on any endurance checks provoked during the duration of the spell as a result of the elements. Because of the weakness of the spell, this bonus can be extended to at most the caster and one other person.

Prestidigitation can be used to teleport fine sized objects about ones person, for example, from one hand to another, from a hand to a pouch or back again, and so forth. It is commonly used for retrieving pinches of spell components from their hiding places.

Additionally, prestidigitation can be used to create small objects – usually no bigger than what can be held in a palm - out of thin air. These objects may appear like anything, but are easily recognized as artificial if held and inspected. They have no significant weight, cannot bear more than a pound of force, have no hardness, no hit points, and automatically fail any break checks. They may however be used to engage in any action that doesn’t require significant force, so for example largely functional needles, magnifying or reading glasses, cups, toothpicks, sponges, hats, quill pens, paper for temporary notes, spoons, and other small tools that are not used with great force can be created. At the end of the spell or whenever they leave range, the objects vanish.

When using prestidigitation to create an appropriate effect, the spell caster may gain a bonus of between +1 and +3 to various skill checks - most obviously bluff, craft, disguise, hide, open lock, perform, sleight of hand, and use rope. The spell caster must explain how the effect he is creating helps in this particular situation, with highly appropriate explanations receiving higher bonuses at the DM’s discretion.

From the above, the answer to your questions are:

1) Per my wording, the object must occupy a 1 cubic foot space. The actual displaced volume of it doesn't matter. It has to still fit inside that hypothetical box.
2) Per my wording, you are essentially given a minor circumstance bonus to your saves or skill checks pertaining to environmental effects during the spells duration. In other words, it helps a little if you are using prestidigitation to keep yourself warm or cool, but by no means gives you immunity. That's easy to translate into 3e, but in 5e it gets a bit trickier. The intended effect is less than the effect of gaining advantage, and certainly shouldn't be larger than gaining advantage.

Of course, while I think my rulings are reasonable, if you aren't the GM asking these questions, you can really only go to your GM and ask what his rulings are. My rulings by no means bind anyone in any edition. They are just clarity for me and my table so that these sort of headaches come up less frequently.
 
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