Sprickan skapades dels av luftbubblan, dels av bränningen.

Dels ... dels ... is a paired expression. Here it means partly ... partly ... or both because of ... and because of ....

So:

• dels av luftbubblan
• dels av bränningen

means that both factors contributed to the crack.

A very natural English rendering is:

• partly because of the air bubble, partly because of the firing
• or caused both by the air bubble and by the firing

It does not usually have the contrastive feeling of on the one hand ... on the other hand.

Because it is a passive verb form.

• skapa = to create
• skapade = created
• skapades = was created

So Sprickan skapades ... means The crack was created ...

In Swedish, adding -s to a verb is one common way to make the passive.

Yes. skapades is past tense passive.

A quick comparison:

• skapas = is created / is being created
• skapades = was created

So the sentence is talking about something that happened in the past.

Av often means by in passive sentences.

So:

• skapades av luftbubblan = was created by the air bubble
• skapades av bränningen = was created by the firing

Even though bränningen is not a person, Swedish still uses av here to show what caused the result.

It is repeated for parallel structure and clarity.

The sentence is built as two matching parts:

• dels av luftbubblan
• dels av bränningen

This is the most natural way to use dels ... dels ... here.

You could think of it as:

• partly by the air bubble
• partly by the firing

Repeating av makes each part complete and balanced.

Because Swedish often uses the definite form when talking about a specific thing already known in the context.

Here:

• sprickan = the crack
• luftbubblan = the air bubble
• bränningen = the firing

The definite ending is attached to the noun:

• spricka → sprickan
• luftbubbla → luftbubblan
• bränning → bränningen

This suggests the speaker means a particular crack, a particular air bubble, and a particular firing process already being discussed or understood.

Here bränningen most likely means the firing process, especially in a technical or craft context such as ceramics, glass, or manufacturing.

It comes from the verb bränna, which can mean to burn or to fire depending on context.

So in this sentence, bränningen probably does not mean ordinary burning in a general sense. It more likely means something like:

• kiln firing
• heat treatment
• the firing stage in production

Sometimes yes, but you should be careful.

In this sentence, both ... and ... is possible in English:

• The crack was caused both by the air bubble and by the firing.

But dels ... dels ... often carries a slight sense of partial contribution. That is why partly ... partly ... can be an even closer match here.

So:

• both ... and ... = good
• partly ... partly ... = often more precise in this sentence

Yes, that would be grammatically possible, but it changes the feel a bit.

• av luftbubblan och bränningen simply lists two causes
• dels av luftbubblan, dels av bränningen sounds more structured and emphasizes that each contributed as a separate factor

So the original sentence is a little more formal and precise.

Yes. Swedish has more than one way to form the passive.

For example:

• Sprickan skapades ...
• Sprickan blev skapad ...

Both are possible, but skapades is more compact and often feels more neutral or written.

In many contexts, the -s passive is the most natural choice.

Yes. luftbubblan is a compound noun.

It is made from:

• luft = air
• bubbla = bubble
• -n = the definite ending

So:

• luftbubbla = air bubble
• luftbubblan = the air bubble

Swedish uses compounds very freely, much more than English learners sometimes expect.

It is most commonly used with two, as in this sentence, but it can be used in longer lists in more formal writing.

For example, Swedish can sometimes pile up several reasons or aspects with repeated dels.

Still, for everyday learning, it is best to remember the common pattern:

• dels X, dels Y

That is the standard and most useful pattern.