Τώρα που τελείωσε η πρώτη όπτηση, αρχίζει η εφυάλωση.

Here Τώρα που means now that. It introduces a situation that has just become true and sets up what happens next.

So the structure is:

Τώρα που + clause = Now that + clause

In this sentence, it means that the first firing has been completed, and as a result the next stage begins.

In this pattern, που links Τώρα to the clause that follows:

Τώρα που τελείωσε η πρώτη όπτηση

You can think of που here as part of the fixed expression Τώρα που, which works like now that in English.

This is a very common Greek construction, even though που has many other uses in the language.

Τελείωσε is the aorist, 3rd person singular, of τελειώνω.

Here it presents the action as a completed event:

• τελείωσε = finished / ended

The subject is η πρώτη όπτηση, so the sense is the first firing finished or the first firing has finished.

Because the sentence describes a sequence:

• first, one stage is completed: τελείωσε
• then, the next stage begins: αρχίζει

This is very natural in Greek process descriptions. Greek often uses the aorist for the completed step and the present for the step that is starting now.

So the sentence is basically saying:

• the first firing is now over
• glazing now begins

Greek often uses the aorist where English might use a present perfect.

So Τώρα που τελείωσε... is very natural Greek, even if in English you might say now that ... has finished.

Τώρα που έχει τελειώσει... is also possible in some contexts, but it sounds a bit more explicitly focused on the present result. In a straightforward description of steps, τελείωσε is the simpler and more usual choice.

Greek word order is much more flexible than English word order.

So:

• Τελείωσε η πρώτη όπτηση
• Η πρώτη όπτηση τελείωσε

both mean the same thing.

Likewise:

• Αρχίζει η εφυάλωση
• Η εφυάλωση αρχίζει

are both possible.

Putting the verb first is very common in Greek, especially in narration, explanation, and process descriptions.

Η is the feminine singular definite article, equivalent to the.

Both nouns here are feminine singular:

• η όπτηση
• η εφυάλωση

So Greek uses η with both of them.

Also, Greek uses the definite article more often than English does. In English, you might say simply glazing begins, but in Greek η εφυάλωση sounds completely natural.

Because adjectives in Greek must agree with the noun they describe in gender, number, and case.

Όπτηση is feminine singular nominative, so the adjective must also be feminine singular nominative:

• masculine: πρώτος
• feminine: πρώτη
• neuter: πρώτο

That is why the phrase is η πρώτη όπτηση.

Όπτηση is a technical word meaning firing, especially in ceramics or similar materials that are heated in a kiln.

So η πρώτη όπτηση means the first firing.

This is not one of the most everyday words in Greek, but it is the correct term in technical or craft-related contexts.

Εφυάλωση is also a technical term. In a ceramics context, it means glazing: the stage where glaze is applied or the glazing process begins.

So αρχίζει η εφυάλωση means the glazing begins.

Like όπτηση, this is specialized vocabulary rather than very common everyday vocabulary.

Not without changing the nuance.

• Τώρα που = now that
• όταν = when

Τώρα που emphasizes that a new situation is now true. It fits well here because the sentence means that one step has now been completed, so the next one starts.

If you used όταν, the sentence would sound more like a general time relationship rather than a specific now that this is done meaning.

Because the first part of the sentence is a subordinate clause:

Τώρα που τελείωσε η πρώτη όπτηση

and the second part is the main clause:

αρχίζει η εφυάλωση

The comma separates them, just as in English:

Now that the first firing has finished, the glazing begins.