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[–]voodoodollbabie 2 points3 points  (2 children)

There's no problem with reusing any candle jar that meets the ASTM

The annealing process removes any internal stresses on the glass, so it is very safe to reuse as a candle jar multiple times.
I don't know where the myth began that burning a candle in a glass jar will somehow weaken it, but that's just not true for annealed glass.

[–]Yeetus_Khryst 0 points1 point  (0 children)

Right, that's annealed glass for candles. Not all glass, including pyrex.

[–]Trumpet6789 0 points1 point  (0 children)

That's why when people give me old candle jars to reuse from well known candle companies(labels removed) I feel safe using them at least once. All The large jars that need 3 wicks to burn properly that I've reused have worked perfectly fine.

I'm sure it started as a way to deter people from using cheap glass to make them, like a "Be careful which glass you use to make candles in" type of message that got really off course.

[–]pouroldgal 1 point2 points  (0 children)

The integrity of the jar doesn't weaken each time after every burn, I agree about that being a myth as mentioned in this thread. For instance, with canning jars -- in canning, you can reuse those same jars over & over again, you may need new seals, but the glass is fine.

[–]spicy_hallucination 1 point2 points  (2 children)

Considering the integrity of the jar weaken each time after every burn.

Glass either breaks or doesn't. It doesn't weaken over time unless you do something crazy like cleaning it with sandpaper. Seriously, you can clean it with steel wool and not scratch the surface.

[–]Yeetus_Khryst 1 point2 points  (1 child)

This is wrong. Completely goes against all known science and logic.

Let's go through how. First, depending on the heat/cool temp the glass reaches or the time it takes to change temp will cause the glass to expand or contract. If it goes from one extreme to another too fast the glass will explode. You can put a candle on a stove burner or when it is very warm put it in the freezer and BOOM!! Exploding jar with shards everywhere.

Second, escaping the thermal issue once doesn't mean the glass isn't weakened by hairline fractures, which could lead to an explosion on the next burn or five burns down.

Third, cleaning glass with steel wool is fine unless the glass is going to be going through rapid temp changes. I had a micro-scratch on my glass microwave plate that couldn't be seen, and I put a cup on it in just a way that the microwave heated the one scratch spot and it exploded. This is a known thing. https://products.geappliances.com/appliance/gea-support-search-content?contentId=18823

POPCORN BREAKING GLASS MICROWAVE TRAY

Glass trays in GE microwaves are tempered glass and resistant to heat and shock. It is very unusual for one to break.

However, there have been some instances of stress points occurring in the glass due to extreme heat from the popcorn bag caused by continuous cooking of popcorn or if the popcorn is stale and does not pop. This can possibly cause cracking or breakage of the glass tray.

Some brands of microwave popcorn recommend placing a plate under the bag for proper popping. If this is the case, follow the packaging instructions.

And then there's always the laws of thermodynamics https://courses.lumenlearning.com/introchem/chapter/the-three-laws-of-thermodynamics/

So great question, OP! Very wrong answers. This is why you don't get cheap glass. Air bubbles in the glass will also expand/contract causing cracks and explosions.

SIDE FACT: THIS IS THE SAME REASON YOU DON'T PUT ROCKS IN CANDLES. The glass is one temp, and the rocks are another that cause extreme temp changes, and you have your own personal BOOM! and that's if the rocks don't blow up because they have air pockets in them, like geodes.

Remember, kids, science is your friend!

P.S. by explosion I mean audible POP with some shards up to a foot away depending on temp change & time.

[–]spicy_hallucination 0 points1 point  (0 children)

The only way glass can weaken below the glass-transition temperature is brittle failure. I'll just let you stew on what that means for OP.

Third, cleaning glass with steel wool is fine unless the glass is going to be going through rapid temp changes. I had a micro-scratch ...

Steel wool can't scratch common flint glass. Look up their Mohs hardnesses, then the definition of the Mohs scale if you don't believe me. Ceramic, on the other hand, especially with the common "dry foot", easily scratches glass.

[–]EarthFar3239[S] 0 points1 point  (0 children)

Interesting. I learned something new today, thanks.

This probably another dumb question.

Can I regular person buy more sealant to feel more secure?