Заготовка треснула, оттого что керамическую массу плохо размяли.

Because it agrees with заготовка, which is a feminine noun.

• заготовка = feminine singular
• past-tense verbs in Russian agree in gender and number with the subject in the singular:
  • masculine: треснул
  • feminine: треснула
  • neuter: треснуло
  • plural: треснули

So Заготовка треснула means the workpiece/blank cracked, with the verb showing that the subject is feminine.

Треснула is past tense of the perfective verb треснуть.

Here the perfective aspect is used because the sentence presents the crack as a completed event/result:

• треснула = cracked / developed a crack
• imperfective трескалась would suggest repeated cracking, ongoing cracking, or a process

So the sentence is about a specific result: the piece ended up cracked.

Оттого что means because.

In many contexts, it is very close to потому что. In this sentence, either would work:

• Заготовка треснула, оттого что...
• Заготовка треснула, потому что...

A few useful notes:

• потому что is generally the most common everyday way to say because
• оттого что can sound a bit more literary, explanatory, or formal
• learners should recognize it as a fixed conjunction here, not try to translate it word by word

So in this sentence, just understand оттого что as because.

Because оттого что introduces a subordinate clause.

The sentence has two parts:

1. Заготовка треснула
2. оттого что керамическую массу плохо размяли

The second part explains the reason, so Russian separates it with a comma, just like English often does with a because-clause.

Because it is the direct object of размяли.

The verb размять means something like to knead, to work through, to mash up thoroughly, depending on context. What was kneaded? Керамическую массу.

Compare the forms:

• nominative: керамическая масса
• accusative: керамическую массу

Both the adjective and noun change because the whole noun phrase is feminine singular accusative.

Literally, it means ceramic mass, but in English that is not always the most natural translation.

In ceramics, керамическая масса usually refers to the prepared ceramic material, clay body, or ceramic mixture/paste used for forming an object.

So depending on context, it might be translated as:

• ceramic mass
• ceramic mixture
• clay body
• ceramic paste/material

For a learner, the key point is that it is the material the object was made from.

This is a very common Russian pattern: a 3rd person plural past-tense verb with no stated subject can mean someone / people / they in a vague, indefinite way.

So:

• плохо размяли literally = they kneaded it badly
• but in natural English, it often becomes passive:
  • it was kneaded badly
  • the material was not kneaded properly

Russian often uses this indefinite-personal construction where English prefers a passive.

It does not point to specific people. It just implies that whoever was preparing the material did it badly.

This is similar to English sentences like:

• They did it wrong
• They mixed it badly

where they does not mean a particular group already mentioned. It simply means someone responsible for the process.

Because размяли is perfective, while мяли is imperfective.

• мяли = were kneading / kneaded repeatedly / were in the process of kneading
• размяли = kneaded through, finished kneading, worked it thoroughly

In this sentence, the bad preparation is presented as a completed cause that led to the crack. That is why perfective размяли fits well.

Also, the prefix раз- often adds the idea of doing something thoroughly or working something through.

It means kneaded badly, did not knead properly, or worked the material poorly.

The adverb плохо modifies the verb:

• плохо = badly / poorly
• размяли = kneaded/worked through

So the idea is that the ceramic material was prepared incorrectly, and that caused the defect.

That is the normal position for an adverb in Russian: it usually comes before the verb it modifies.

So:

• плохо размяли = kneaded badly

Russian word order is flexible, but this order is neutral and natural.

Yes. Russian allows that.

For example:

• Оттого что керамическую массу плохо размяли, заготовка треснула.

This still means the same thing: Because the ceramic mass was kneaded badly, the workpiece cracked.

The original version starts with the result and then gives the cause. That is a very natural way to present it.

Not always. Заготовка is a broad technical word meaning a piece prepared for further processing.

Depending on context, it could be:

• blank
• workpiece
• preform
• rough piece
• green body or similar, in a ceramics context

So the exact English word depends on the field. For learning Russian grammar, the important point is that it is the item that cracked.

Yes, and that is often the most natural choice.

A very literal version would be:

• The workpiece cracked because they kneaded the ceramic mass badly.

But more natural English in a technical context might be:

• The workpiece cracked because the ceramic material was kneaded poorly.
• The piece cracked because the ceramic mass had not been kneaded properly.

This is a good example of how Russian often uses an indefinite they where English prefers the passive.

Yes. Learners should know that оттого что in this sentence is a fixed conjunction meaning because.

That is different from the literal combination от того, что:

• оттого что = because
• от того, что = literally from that which / from the fact that, depending on context

In your sentence, it is the conjunction оттого что, so just read it as because.