HI, Id like to decorate used jars that have previously had jam and sauce etc in them, and Id like to add a tea light inside.
But Ive come to the conclusion that when the candle burns it may release the smell of what was previoulsy in it which wont be good if it was something pongey.
Ive been submerging the jars in boiled water to clean them/hopefully get the smeel out. Do you think that will do the trick?
Any help appreciated.
If you pop them in the oven and gradually turn up the heat over 45 mins until is as high as it’ll go you’ll sterilise the jars and get rid of any nasty smells. I do this when I’m getting jars ready for jams and chutneys so there’s no taste left in them either 
I would personally be wary about selling items that were intended to be used with naked flames in our litigious society.
Following on from Sonia’s comment you would need to consider how are people going to get the lit tea light safely into the jar or how are they going to light it in the jar without running the risk of burning their hand. You would also need to consider the paint - is it safe up to the temperatures that the glass might get to near the tea light/ candle? (is it going to become tacky to touch or release fumes). Sorry to put a bit of a dampner on your creative ideas.
To answer your original question, soaking in a percarbonate bleach (vanish or equivalent) and then running through the dish wash to rinse any traces off would do the trick. (as would sodium hypochlorite bleach but percarbonate is nicer to handle, I spent years as a chemist getting smells off glasswear…)
You’ll need to use glass paints so the heat will not destroy the paint as you fire them in the oven first once you’ve painted them.
You use the extra long matches to light the tea light or you’ll scorch your fingers if the jar in too deep and/or narrow.
I make my own for the house at Christmas Time.
Also you can make candle in the jars so the wick is at the top of the jar.
And yes I soak jars in hot soapy water and give them a good scrub rinse and leave to dry then into the oven to sterilize them. I put mine onto trays as it’s easier to get them in and out again.
I leave them in the oven for about 10 minutes after I turn it off just incase the sudden drop in tempeture fractures the jar.
I use this method both for my candle jars tea light jars and for making preserves.
If you want to bring the tea light up you can provide little bags of coloured sand to place into the botton of the jar so the tea light comes up a bit closure to the top of the jar and the colours looks pretty.
I sometime buy floating candles and pour water into the jar about halfway with some coloured beads or flower arranging coloured glass pebbles at the botton and the overall effect is so pretty.
I’ve even put tiny springs of holly into the water in the glass jars with the floating candle.
Thanks for your replies.
I was inspired by seeing decorated jars in a garden centre.
Maybe your right and candle jars arnt such a good idea to sell.
I did some googling and washing them in denture cleaning tablets works apparently.
Maybe il stick to my other idea of dioramas in jars.
@GrimmExhibition You could always decorate the jars and sell them with the suggested the use of putting small flower arrangements in on the christmas table (or something similar). If they then want to put a candle in it (as well as or instead of the flowers) then they can choose to do so but if they injure themselves in the process they can’t blame you as you did not suggest the useage or supply the candle (but I am not a laywer so that may not be accurate). Remember that cups of take away coffee etc have printed on them ‘caution contents may be hot’ because someone once sued a company after scalding themselves of a hot beverage and they hadn’t been warned that this could happen (common sense doesn’t stand up as an arguement in court apparently). That said I’m liking the idea of the diorama - could you turn it into a snow globe I wonder?
Its crazy isnt it. If I did make jar candles Id supply a decorated jar and a tea light candle but at no point are those things dangerous until a lit match is added!!(which I wouldnt supply) yet id still get the blame if anything went wrong.
Love the flower vase idea, may give that a go as I have a load of jars. I could put holly in it.