Glas vs. Einmachglas
In German, both Glas and Einmachglas can translate to the English word "jar", but they refer to different types of containers. The distinction lies in whether the container is a general, everyday commercial jar or a specialized jar explicitly meant for home preserving.
Glas
The word Glas is a broad, versatile term that serves as the general word for "jar". In the context of containers, it refers to a standard, commercially produced glass jar that you would buy at a grocery store holding items like jam, pickles, or pasta sauce. It is also the standard word for a drinking glass or the material glass itself.
Ich habe ein neues Glas Honig auf dem Markt gekauft.
(I bought a new jar of honey at the market.)
Kannst du mir bitte helfen, dieses Glas mit den Oliven zu öffnen?
(Can you please help me open this jar of olives?)
Bitte wirf das leere Glas in den Container für Altglas.
(Please throw the empty jar into the recycling bin for glass.)
Wir bewahren unsere Haferflocken in einem großen Glas auf.
(We store our oatmeal in a large jar.)
Im Kühlschrank steht noch ein halbes Glas Mayonnaise.
(There is still half a jar of mayonnaise in the fridge.)
Einmachglas
The word Einmachglas translates specifically to "mason jar", "canning jar", or "preserving jar". It describes a sturdy, specialized jar designed specifically for home canning, pickling, and preserving food, usually equipped with a special sealing mechanism like a rubber gasket and metal clamps, or a specialized two-piece lid to create a vacuum seal.
Meine Tante kocht im Herbst Früchte ein und füllt sie in ein Einmachglas.
(My aunt stews fruits in the autumn and fills them into a preserving jar.)
Für dieses Rezept benötigen wir ein gründlich sterilisiertes Einmachglas.
(For this recipe, we need a thoroughly sterilized mason jar.)
Der Gummiring für das Einmachglas fehlt, deshalb schließt es nicht luftdicht.
(The rubber ring for the canning jar is missing, therefore it does not close airtight.)
Er fermentiert seinen eigenen Rotkohl in einem großen Einmachglas.
(He ferments his own red cabbage in a large mason jar.)
Im Keller meiner Großeltern stehen hunderte Einmachgläser mit eingelegtem Gemüse.
(In my grandparents' basement, there are hundreds of preserving jars with pickled vegetables.)
Summary
To summarize, use Glas when you are talking about any standard, everyday jar, such as the ones you buy at the supermarket or use for casual storage. You should use Einmachglas when you are specifically referring to a mason jar or a canning jar equipped to preserve, pickle, and vacuum-seal homemade foods.