Learn Farsi: خاک را ورز دادم تا سفالگر رسید. - I kneaded the clay until the potter arrived.

In this sentence, تا means 'until' and describes a completed event in the past (the potter actually arrived). When تا refers to a fact or a completed past action, we use an indicative tense like the simple past. We would only use the subjunctive if we were talking about a future or uncompleted event, like 'I will knead the clay until he arrives'.

Doesn't خاک (khâk) usually mean 'dirt' or 'soil'?

Yes! خاک is the general word for dirt, earth, soil, or dust. However, in the context of pottery, it refers to the raw earth or 'clay' being prepared. You might also see خاک رس specifically for clay, but just خاک is very common when the context makes it clear.

Why do we need را (râ) after خاک?

را is the specific direct object marker. Because you are kneading a specific batch of clay ('the clay' rather than just 'some clay'), you need to add را right after the noun to show that it is a known, specific object receiving the action.

What is the infinitive of ورز دادم (varz dâdam)?

The infinitive is ورز دادن (varz dâdan), which means 'to knead.' Like many Farsi verbs, it is a compound verb, made up of ورز (kneading) and دادن (to give). Here it is conjugated in the simple past for the first person 'I' (دادم).