Skuimgehalte verbeter nie soseer weens warm melk nie, maar weens stoomdruk.

It is a fixed contrast pattern meaning not so much ... but rather ....

So the sentence is saying that foam quality improves not so much because of warm milk, but because of steam pressure.

An important nuance: this often does not mean the first thing is completely false. It usually means the second thing is the more important or more accurate explanation.

Afrikaans normally uses double negation.

In this sentence, the pattern is:

nie soseer + reason 1 + nie, maar + reason 2

So:

• the first nie starts the negative contrast
• the second nie closes it
• maar then introduces the corrected or stronger alternative

English usually needs only one negative here, but Afrikaans often needs two.

Soseer is an adverb that means something like so much, to such an extent, or particularly.

In the expression nie soseer ... nie, it gives the idea not so much.

So in this sentence, nie soseer weens warm melk nie means not so much because of warm milk.

Weens means because of, due to, or owing to.

It is correct and natural, but it sounds a bit more formal or written than some everyday alternatives.

Here it introduces the cause:

• weens warm melk = because of warm milk
• weens stoomdruk = because of steam pressure

Usually no. Weens is a preposition, so it normally takes a noun phrase, not a full finite clause.

That is why the sentence has:

• weens warm melk
• weens stoomdruk

If you want to say because the milk is warm, Afrikaans would usually use something like omdat instead of weens.

Afrikaans, like Dutch and German, often writes compound nouns as one word.

So:

• skuim = foam
• gehalte = quality

Together, skuimgehalte means foam quality.

A useful rule: in these compounds, the last part is usually the main noun, and the first part describes it.

Because both are being used in a general sense, not to refer to one specific item.

Afrikaans often leaves out the article with:

• mass nouns, like melk
• abstract or technical causes, like stoomdruk

So weens warm melk means because of warm milk in general, not because of the warm milk.

Because Afrikaans main clauses usually follow the verb-second pattern.

In a normal statement:

• first comes one sentence element
• then the finite verb comes second

Here:

• Skuimgehalte = first element
• verbeter = second element

So the word order is completely normal for Afrikaans.

Maar means but, but in this structure it is doing more than simple contrast. It introduces the better explanation or corrected focus.

So:

• nie soseer weens warm melk nie
• maar weens stoomdruk

means:

• not so much because of warm milk
• but because of steam pressure

In English, but rather is often a good match.

Not necessarily.

The structure nie soseer X nie, maar Y usually means X is not the main reason; Y is the more important reason.

So the sentence does not have to mean that warm milk plays absolutely no role. It mainly says that steam pressure is the real key factor.

Yes. Depending on style, Afrikaans might also use:

• vanweë = because of / owing to
• as gevolg van = as a result of
• sometimes oor, depending on context

But weens works well here, especially in a more technical or explanatory sentence.

It sounds slightly formal or technical, mainly because of:

• weens
• the noun skuimgehalte
• the careful contrast structure nie soseer ... nie, maar ...

It is still perfectly natural Afrikaans, but it sounds more like explanation, instruction, or technical discussion than casual conversation.