jeniryan Posted November 30, 2007 Share Posted November 30, 2007 I've had two jars crack this week after pouring. I'm pouring other candles at the same time, same temps, same amount, etc. I heat my jars prior to pouring. Is this just one of those things that happen sometimes, or is it something I may be doing? Thanks! Quote Link to comment Share on other sites More sharing options...
islandgirl Posted November 30, 2007 Share Posted November 30, 2007 What type of Jar is it??? Is it a thin glass jar?I have never had a jar crack after pouring, but I use mason jars which accept high heat. That would make me very nervous and worried about the other jars in that batch. I would call your supplier and ask. This is not something you want to mess around with. Quote Link to comment Share on other sites More sharing options...
logcabinmomma Posted November 30, 2007 Share Posted November 30, 2007 I've only ever had 3 jars EVER break. One was after heating in the oven on too high a temperature (was melting down remaining wax to reuse the jar to test- this jar had been heated and cooled many times already). By the time I got it out of the oven, the bottom had cracked. One was from falling out of the back of my van going to a show (ick). The last was from dropping on a tile floor.Aside from trauma, a new jar should never break. I would contact your supplier and return the entire shipment. It's unacceptable to have jars break while pouring. Even my flimsiest glass that I chose not to carry never did that. How many jars did you pour that 2 of them cracked when pouring? How hot are you heating your jars prior to pouring? Sounds really bad!-Kristi Quote Link to comment Share on other sites More sharing options...
jeniryan Posted November 30, 2007 Author Share Posted November 30, 2007 They're 8 oz jelly jars from JBN. I called to ask them about it and to let them know, which they said they've never heard of that happening before. Of course, they said this time of year the jars need to be warmed, which, I told them I did. So.... guess maybe it's just a weird fluke thing... Quote Link to comment Share on other sites More sharing options...
jeniryan Posted November 30, 2007 Author Share Posted November 30, 2007 I turn my oven on to 170( which is the lowest it will go) then turn it off and put the jars in. I only leave them in for a couple of minutes and make sure they are warm to the touch when I remove them. The cracking is on the side of the glass, horizontally. It was 2 out of a dozen that cracked. I'm pouring at about 155, definitely not too hot. So, I just don't know..... Quote Link to comment Share on other sites More sharing options...
logcabinmomma Posted November 30, 2007 Share Posted November 30, 2007 How hot are you heating them in the oven? Can you stick a thermometer in there to see how hot they're getting? Perhaps they're getting too hot first? If it's the first they've heard of it, most likely it's something that either happened to only your batch of jars (dropped somewhere or something) or a factor that's happening in your production (heating too hot first is all I can think of).-Kristi Quote Link to comment Share on other sites More sharing options...
VerticallyEnhanced Posted November 30, 2007 Share Posted November 30, 2007 and the are ones that you have NOT used for testing?? i.e. fresh jars...ones that have never had candles poured in them? If yes, then I would be very nervous...as islandgirl said, it could be a flaw in the lot. In all the years I have done this, the ONLY jar I have ever had crack was one someone wanted me to fill that they had burned a LOT of candles in. It was the same as mentioned above...it had been heated/cooled many times over. Because of that, I don't do fills in customer's jars. Quote Link to comment Share on other sites More sharing options...
Stella1952 Posted November 30, 2007 Share Posted November 30, 2007 ALL glass cracks and breaks and shatters. Having said that, jars used for canning are usually good candidates for candlemaking because they are designed to handle temperatures in excess of 212°F. Most candlemakers are not home canners (or they would have learned the hard way years ago about glass jars) and may be unaware of proper jar handling guidelines:1. NEVER allow jars to rest on direct heat. This is why water bath canners and pressure canners have inserts to hold the jars OFF the bottom of the pots. A jar sitting directly on the bottom directly over the flame or heating element, even surrounded by water, is subjected by direct heat transference to much greater temperatures than the surrounding water. Even thermostatically controlled devices such as griddles and Prestos cause problems because the ELEMENTS are either ON or OFF - this means that when on, the area over the element is MUCH hotter than the setting of the thermostat. The result is typically seen as a crack around the bottom of the container and is caused by thermal shock. Canning jars are thicker on the bottom, which means that that area will not expand/contract at the same rate as the rest of the jar. It is designed to prevent cracking from being bumped on the bottom, but is a problem for thermal shocking of the glass. Thick glass is NO GUARANTEE against thermal shock. That is a MYTH! In fact, thicker glass oftentimes will crack more easily as it doesn't change temperature as quickly as does thin glass, and is more succeptible to thermal shock for that reason. Containers with thick and thin areas are prone to thermal cracking where the thicker area meets the thinner area.2. Jars should be heated only to the point that they are warm to the touch. You should ALWAYS be able to pick one up without burning your hand. If it's too hot to touch, the container has been overheated. Heating in ovens has to be done with care and ALWAYS with the jars sitting on a rack rather than directly on a pan. Even Pyrex recommends never placing an EMPTY dish or container in the oven to warm because of this. When heating jars in the oven, the oven should be COLD when they go in! If it is already warm, one is placing cold glass into a much warmer environment, which can again stress the glass and allow thermal cracking. USE A THERMOMETER IN THE OVEN!!!3. Prewarmed jars should be placed on racks or thick towels. There is a LOT of difference in the temperature of a hot jar and a kitchen countertop! This is a major cause of bottom cracks. I put my jars in the oven and onto the counter in the cardboard box in which they were purchased. The oven should not be hot enough to cause the paper to burn and the cardboard will help insulate the bottoms from thermal shock.4. Jars should be cooled on racks or thick towels to allow the container to cool evenly. Setting a hot jar of wax on a cold countertop is asking for trouble, not only with the container cracking, but with the wax inside not cooling evenly.I realize and fully expect some folks to reply that they have never followed the procedures above and never had a jar crack. They can thank the integrity of their products for compensating for their poor glass handling practices. It's product quality and LUCK that they have not had a problem. Follow the proper handling guidelines and you will seldomly have trouble. There is a reason that canning jar manufacturers make these recommendations! Quote Link to comment Share on other sites More sharing options...
jeniryan Posted November 30, 2007 Author Share Posted November 30, 2007 NO, I bought them brand new, never used them prior for anything. I have two candles burning now from the same lot of glass, no problems with them so far.... Quote Link to comment Share on other sites More sharing options...
jeniryan Posted November 30, 2007 Author Share Posted November 30, 2007 I never would've thought to use the box the jars came in to heat them in. That's a really good idea! But now this leads me to another question. I've seen posts saying that some people actually let their candles cool in a warmed oven turned off, what do they have their candles on? Just the oven rack? I'm certain that I didn't overheat the jars, as I could handle them by hand with no protection. Now, I did have them on a cookie sheet to heat, because it is just easier to get them in and out that way... I didn't know any better I don't guess.... Live and learn, I suppose Quote Link to comment Share on other sites More sharing options...
Stella1952 Posted November 30, 2007 Share Posted November 30, 2007 I use an old sheet cake pan with a cookie rack inside that the jars set on. Having done a lot of canning, I can tell you that there are always a few containers here and there which will crack even with the best of handling (remember: glass BREAKS no matter WHAT!). If I had several crack from the same case, I would suspect that this was a bad case and I would report this to the folks from whom I bought them.Once again, a jelly jar is not a jelly jar is not a jelly jar. The ones manufactured by Ball, Kerr, Mason, etc. are made according to US standards. There are a LOT of "look alike" canning jars imported from China which are NOT reliable. Saving a little money on inferior containers will cost more in the long run than buying a more expensive brand-name product. I LOVE our suppliers, but no way would I purchase canning jars from them! The shipping would eat me up and I can buy cases and cases of canning jars from WalMart, the grocery store, hardware store, Feed & Seed, etc. LOCALLY. If a case is defective, it gets returned easily and quickly. Quote Link to comment Share on other sites More sharing options...
kandlekrazy Posted November 30, 2007 Share Posted November 30, 2007 I make jellies and jams and even following the proper procedures of sterilizing and pouring into hot jars, I still will have one or two pop and crack every once in a while. I don't use these jars for candles, but Stella is right on...any glass can crack or shatter under heat, pressure or even cold. That's why we take every precaution to test that our containers do not get too hot while burning. Jars may have stress cracks or weak points that you cannot see and sometimes it's nothing you did wrong, it just plain cracks! Quote Link to comment Share on other sites More sharing options...
logcabinmomma Posted November 30, 2007 Share Posted November 30, 2007 When I first started making candles, I made them in the Ball canning jars that are widemouth and good for freezer or canning use. They are a tempered glass made for extremes and I NEVER had one break. I bought them by the case from Ace Hardware (who carries them year round). And the 8 oz and 16 oz are the same size diameter and opening and makes them super easy to wick...-Kristi Quote Link to comment Share on other sites More sharing options...
jeniryan Posted November 30, 2007 Author Share Posted November 30, 2007 I just noticed that JBN has 8oz mason jars so I'll have to give them a try. When I called to ask about wicking for them, they recommended I go up one to the RRD - 47. I may give the CDN's a try also, I've never used them at all so I'll have to figure out what size to go with there. Guess I'll be making a trip to JBN on Monday! Thanks for all the tips guys! Quote Link to comment Share on other sites More sharing options...
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