thimble of mending clothes
Basically when you wear this thimble you can repair ANY peice of clothing in 24 seconds,though you must have the gift to mend magical clothing in that amount of time,otherwise it takes 24 hours to fix magical clothing.
I'm not seeing this as a lab item, sir, but it could be useful to the covenant. You would need a breakthrough to repair magic clothes in less then a season though, and you would still need to put that virtue into the item. Tricky. If you are looking for lab items, why not a magic bathroom, to increase the health rating of the lab?
The magic bathroom idea acturally could work!
Could not resist:
Anybody else thinking of Hogfather ... ?
Not before your mention no...
How about a magic sack that produces coal then?
That's pretty easy, for something that Hermetic magic can't do. You will need the virtue of Runic Magic, the "easiest" Ancient Magic to find and research. The Bag of Coal will then take a season, at best.
for a mage trying to transform a risky lab into a any other lab-the cricket of warning!
when a explosion occurs the cricket sends out a warning shout in time to prevent the mage from taking any damage.
advanced versions could give enough warning to prevent the explosion from occurring at all!
Not at all. Just have the bag constantly refill itself with coal that lasts for a duration of Sun. Unlimited use, Environmental Trigger (when the bag is not full). The coal only needs to last long enough to be burned. What's better is that when the coal expires, after it was burned, the soot and residue of the coal disappears. The heat provided is constant because new coal is being burned, and a new layer of soot and residue forms but there is no build up.
Come to thing of it, why not skip a step and have the furnace constantly provide itself with fule? It would be even better to just use Ignem, but if Terram or Herbam is your strong Art you may want to go this route.
Yes, but at that point we are getting away from the bag of coal, and a bag of coal with duration sun can't be used to give coal to bad little kids.....
actually the coal was for heating the lab mostly.
I was also thinking about heating the lab 
. But if you want to go that route, I have another way. Farie Magic, since your idea sounds somewhat like a faerie idea. As a spell, use Until-Condition, the condition being Until the bad child behaves himself (make it muto, changing a toy to coal so when he becomes good he gets a present). Since it is a Ritual, you would have to use Hermetic Empowerment to invest it as an item.
I think some people have the view that you can use unique parameters in Formulaic spells, so a normal Hermetic Magus could use Until Condition at the cost of an additional magnitude. I am not sure about that, though I like the idea. What do other people think?
Well, to heat the lab, creo ign, room will do the job without the nasty coal fumes. I like the until condition, but Faerie Magic is easy to learn, so I wouldn't allow the end run. I mean, they're like the Seven Up of mystery cults. Point of faerie warping and ask.
for double the lab work,how about the nightcap?
this item allows the wearer to go without sleeping for up to 5 moons at a time & see in the dark!
Oh, not good. You won't get double, you'll get what, +10 to your lab score, and in return you get warping points and aging rolls. Just say no.
If they´ve had a chance to learn it, yes. Though it can be argued of course that unique parameters tied in to something needs the "tie-in" before you can learn it. Id say canon does not strictly require it.
Mmm, and that is why magic food without ritual should work as well. 
Slightly different. Just as the residue and soot disappears when the coal expires, the nutrition and vitamins of the food disappears when that spell ends. You can't undo all the energy you recieved from the food, you used it running around . But the sudden loss of nutrition is the kicker. There is no harm to a furnace when it suddenly lacks soot and resin.
Ah but then the argument can easily be that you are adding a modern concept and modern knowledge to make a special case.
And either way, if long enough duration is picked, it would have been mostly used up anyway.
Unless of course you want to be nasty about it, then any person having survived on magic food for a long time will simply disappear at the end of duration.
As I am a gentle SG, I would be easilly swayed into handwaving it and say you just need to eat double portions for a number of days equal to the time you were sustained by magical non-permenant food.
This thread is for lab items fyi!!!!