На ангобе появились трещины, оттого что обжиг начали рано.

Ангобе is in the prepositional case singular.

Here на means on the surface of, so на ангобе means on the engobe/slip layer. That fits the idea that the cracks appeared on the coating.

• на ангобе = on the engobe
• в ангобе = in the engobe

So if the speaker means the surface layer itself developed cracks, на ангобе is the natural choice.

Both are possible. Russian word order is much freer than English word order.

• Трещины появились is more neutral if you are simply stating the subject first.
• Появились трещины often presents the cracks as newly appearing information: literally something like there appeared cracks.

So the sentence starts with the event/result, then names what appeared. This is very natural in Russian.

Because the subject is трещины, which is nominative plural.

In the past tense, Russian verbs agree with the subject in number and, in the singular, also gender:

• трещина появилась = a crack appeared
• трещины появились = cracks appeared

So появились matches plural трещины.

Появились is the perfective past of появиться.

Perfective is used because the sentence refers to a completed event/result: the cracks appeared.

Compare:

• появились = appeared, came into being
• появлялись = were appearing / used to appear / appeared repeatedly

Here the focus is on the fact that the cracks came into existence, so perfective is the normal choice.

It is nominative plural, because трещины is the subject of появились.

The verb появиться is intransitive, so it does not take a direct object here. The cracks are not something being acted on; they are the thing that appeared.

So the structure is:

• появились = appeared
• трещины = cracks

Оттого что and потому что can both mean because.

In many contexts they are interchangeable, but оттого что can sound a bit more literary, bookish, or explanatory. It often has a slight sense of as a result of the fact that.

So:

• потому что = because
• оттого что = because / from the fact that

In this sentence, оттого что is perfectly natural and slightly formal in tone.

Because here it is a conjunction made up of two parts:

• оттого
• что

Together they introduce the reason clause: because...

So in this sentence:

• На ангобе появились трещины, оттого что...
• Cracks appeared on the engobe because...

Learners sometimes expect one solid word, but in this use it is written as two words.

Because оттого что обжиг начали рано is a subordinate clause of reason.

Russian normally places a comma before conjunctions that introduce subordinate clauses, including:

• потому что
• оттого что
• так как
• когда
• если

So the comma is required here.

Обжиг начали literally means they started the firing. This is a very common Russian pattern where the doer is left unspecified.

Russian often uses a 3rd person plural verb with no explicit subject to mean something like:

• they
• people
• someone

So:

• обжиг начали рано = they started the firing early
• обжиг начался рано = the firing began early

These are close, but not identical.

Обжиг начали рано emphasizes that someone started it early.
Обжиг начался рано presents it more as an event that began early.

Обжиг is a masculine noun. It means firing in a ceramics context.

In this sentence it is in the accusative singular, but for this noun the accusative looks the same as the nominative:

• обжиг = nominative singular
• обжиг = accusative singular

Why accusative? Because it is the direct object of начали:

• начали что? — обжиг
• started what? — the firing

Literally, рано means early.

In context, however, it often implies too early if the result was bad. Since the sentence says cracks appeared because the firing was started early, the meaning is naturally understood as earlier than it should have been.

Compare:

• рано = early
• слишком рано = too early
• раньше = earlier

If the speaker wanted to make the idea completely explicit, they could say слишком рано, but рано is often enough when the context already shows it was a mistake.

Yes. A very natural alternative would be:

На ангобе появились трещины из-за того, что обжиг начали рано.

This also means because the firing was started early, but it can sound slightly more like due to the fact that or because of.

Very roughly:

• потому что = because
• оттого что = because / from the fact that
• из-за того, что = because of the fact that

All are possible, but each has a slightly different tone.

It sounds fairly neutral to technical, mainly because of the vocabulary:

• ангоб
• обжиг

Those are specialized ceramics terms, so the sentence feels like something from a workshop, manual, or technical discussion.

Grammatically, though, the sentence is normal standard Russian. The only slightly bookish element is оттого что, which is a bit less conversational than потому что.