User FAQ

Professionals answer your questions

In the following you will find our user FAQ and the according advices and tips. The content is based on the category "preserving service" of the magazine "WECK® LandJournal".

If you have any questions or helpful tips don't hesitate to write us on our Facebook page.

Apples rising in jar

„I preserved apples, therefore I used round rim jars fully filled with a sugar mixture. After preserving one part was ok, but on the other hand nearly one third of the liquid went out of the jar. The apples are now swimming at the top of the jar and are no longer covered by the sugar mixture. The jars are completely closed. What did I do wrong? And do the apples remain intact anyway?

Ruth B., via e-mail

Apples, like much other kinds of fruit, generate at a specific degree of ripeness an upswing while heating up and they press air and liquid out of the jar. During the cooling time the content contracts itself with the result you describe. There is no derogation of the storage life. To solve this problem you should slowly heat the water while preserving. Another reason may be that there is too much food in the jar. Air chambers may arise and they can't be filled by sugar or vinegar mixtures. In this case stack your food in a more loose way

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Half filled jars

„I ran out of small jars, but I would like to preserve only a small quantity. Is it possible to use large jars and just fill them half of the top?“

Marga R., via e-mail

Even if the jars are only filled moderately a vacuum can be caused as a certain amount of air will be squeezed out when heating up the filling good. Because of the oxygen left in the jar oxidation will begin and this may change the colour of the food within the jar and nutrients may get lost. Some may remember this occured often in former times as in the "old" solid rim jars oxygen was left under the lid. The upper layers of e.g. pears, apples or apple sauce changed their colour to brown. Following the advice of nutritionists the new round rim jars are configured for optimal filling up to the rim so that all air is squeezed off and an optimal vacuum is estabilshed. So the upper layers within the jar no longer change their colour. 

Pasty food like apple puree, greasy sausages and meat dishes need some space for expansion, i.e. 2 to 3 cm below the rim. In exceptional cases it's possible to fill only the half of large jars, but for best results we recommend to adapt the size of the jar to the quantity you intend to preserve.

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Jars burst

„Yesterday I used my WECK® jars for baking again. I made a cherry crumble which had to be baked at 200° C in the oven. After having taken the jars out of the oven and having covered the cherry crumble with vanilla sauce I could watch the jars bursting. How cound that happen?

Nadine G., via e-mail

Preserving jars are not "fireproof" although they can be heated up to more than 100° C. Their melting point is about 830°C! Anyway they don't like thermal shocks as they them burst. Preserving jars have a thermal shock tolerance of about 50°C to 60°C. That means you have to put the jars out of the oven onto a proper underlay (e.g. a folded towel) for cooling before you serve it with a cool or cold vanilla sauce.

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Heating time in a preserving pot

„It nearly takes 30 minutes until the warning light of the half-filled preserving pot expires. Is that ok? I don't intend to preserve the food too long.“

Christa S., via e-mail

A long heating time is unavoidable because a large volume must be heated with a small real power. The reason for this defined small real power is that the temperature of the jars content needs more time for heating up than the surrounding water. If the water was heated up too fast the control light would signalise that the preserving process already began even if the required temperature in the jars wasn't yet achieved. The consequences are that the jars won't close and the content perishes. Moreover the food may stick under the lid and the creation of a vacuum in the jar is at risk. Please respect the proofed times and temperatures for preserving. The combination of heating and cooking time will be successful.

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Microwaving preserved food

„I would like to microwave preserved food or a half-baked cake in a jar. Is that possible?“

Yukiko S., via e-mail

Preserving jars are ideal for microwaving if you start the heating process at room temperature. That means that jars taken out of the fridge or the freezer shouldn't be heated directly. That would cause a thermal shock. Instead they must be heated slowly until they achieve room temperature. This also applies before putting them into the preheated oven or by taking them out of the pot and placing them onto a cold underlay. 

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Rubber pull demolished

„It often happens to me that the rubber pull is demolished while opening a perfect preserved jar. I stopped trying to open it with screwdrivers or other instruments because rather the jar may break before I receive the content. Do you have a tip for me?“

Peter B., via e-mail

You acted properly stopping to use screwdrivers and knifes because there is a high risk of injury. If a jar doesn't open the first try is to put the clamps on the lid, place the jar upside down in a pot of water and heat it up. The content will enlarge and presses on the lid from the inside so that the vacuum will be extincted. If you now take the jar out of the pot and remove the clamps the jar will be open. Another option are special jar openers offered by retailers. A wire loop has to be placed between jar and lid and tightened with a clamping lever. 

The demolition of rubber pulls is often caused by preserving in the oven. The dry heat makes the rubber rings brittle and fragile.

Another tip: The opening should be executed in the same angle as the pull points; at older jars upwards, at round rim jars downwards. If you pull the rubber horizontally it passes a sharp glass edge. Thus there' always the danger of tearing it.

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Insect protection

„After a pest infestation in our kitchen we are looking for alternative containers to stock grain, rice, flour etc. We have got the idea of using WECK® jars because they are non-toxic, but it seems awkward to me to always use the clamps. Is it possible to use only the WECK® plastic lid or isn't it tight enough to prevent moths or other insects from getting inside?“

Miriam N., via e-mail

Our preserving jars are tight even by using the plastic lid, but you shouldn't use one lid for different contains, because it may adopt the smell, e.g. of spices. The plastic lid is safe as long as it isn't deformed by heat or wrong storage. The preserving jar is no risk to the health. The weight of the glass lid is an effective closure and doesn't require necessarily clamps as the air exchange is guaranteed. Using the rubber ring and the clamps an air exchange is impossible.

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Baking in closed jar

„I read that it's possible to bake cakes in closed jars. Is that really possible? I don't dare to try it.“

Dorothea D., via e-mail

We advise to bake in open jars to get the best result. But baking in closed jars is possible although there are some negative points:

  • While the jar is closed you can't proof the temperature and must depend on the cooking time which is indicated in the recipe. We strongly advise to make the proof if the cake is well baked. Otherwise storage life is not guaranteed.
  • If you bake in closed jars you have to take the exact portion of dough,. Baking in open jars the amount can be adjusted by cutting the dough down to the top of the jar before preserving.
  • The rubber ring may be damaged due to the high temperatures in the oven. It can get prudish or gluey. If you decide to bake in closed jars we recommend you to use a new rubber ring each time.

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Preserving desserts

„The crème brûlée publshed in the September/October issue tastes great. I would like to serve it next time at a party, but want to prepare it in advance and therefore preserve it. Is this possible?“

Sylvia F., via e-mail

We are sad to tell you that it's not possible to preserve the crème brûlée. The preserving jar was just used for portioning, but it's also comfortable to be stored in the fridge. You can prepare the cream 2 to 3 days in advance and store it in the fridge closing the jar with rubber rings, glass lids and clamps.

Generally it's not that easy to preserve desserts, but you can preserve semi-finished products, like e.g. a cake you can cut off a day before the party an decorate with cream and fruit in the jars.

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White film in jar

„I preserved plums and probably filled the jars too full so that a bit of liquid got out, but the other jars are fine. Now I can see at the inside of the glass lid a slight white film. I´m not sure if this is mouldiness or something else, but I don´t want to throw away the whole charge. How can I be sur, whether the plums are still alright? My first thought was to leave the jars standing and to wait the jars to open themselves because of the fermentation gas. Is this a safe method?

Johannes A., via e-mail

Mouldiness on surfaces can have a lot of reasons. Mostly it depends on the temperature. So maybe your content was not heated enough. Preversing fruit 30 minutes with 90°C hot water is a minimum to kill fungal spores. There are more than thousands of kinds and colours of mouldiness spores. Often a slightly white film is determined. Contrary to your assumption mouldiness doesn´t form fermentation gas unlike a lot of other bacteria.

In your case the vacuum inside the jars is stable and the jars are still closed. Stone fruits have a waxy surface. The wax is melting during the heating process. So it's clinging in a white-greyish sort of film to the glass surface. Without being able to look at your jars right now we can't judge the problem. Thus we can't tell you if the white film is mouldiness or a segregation from the fruits. We advise you at first to keep an eye on the jars. The waxy segregations are not changing anymore, but the mouldy places can spread. If this is the case we urgently recommend you to throw away the content of the infested jars, to wash them very thoroughly and to replace the rubber rings.

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Jars are swimming or instable

„It often happens that my jars are swimming or are standing very unsteadily inside my cooking pot. Is there any chance to stabilise the jars?“

Peter A., via e-mail

This phenomenon often occurs especially when you preserve cakes. Absolutely avoid the rising of the jars inside your cooking pot. Rubbing against each other the jars get tiny scratches, which can lead to mechanical stress. Try to weight the jars so they can stand safely. The easiest way to do so: Fill empty jars with water and place them on top of the other jars. This weight should be sufficient to stop the rising.

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