Du moment que l’argile reste souple, on continue.

Here du moment que means as long as.

So:

• Du moment que l’argile reste souple, on continue.
• As long as the clay stays soft, we continue.

It introduces a condition: the action continues provided that the clay is still soft.

Be careful: du moment que is not always translated word-for-word. Even though it looks like from the moment that, in many contexts it really means as long as / since / given that, depending on context.

They are often very close in meaning, especially here.

• Du moment que l’argile reste souple, on continue.
• Tant que l’argile reste souple, on continue.

Both can mean as long as the clay remains soft, we continue.

A small nuance:

• tant que is often the most direct way to say as long as
• du moment que can sometimes sound a bit more like provided that / given that

In this sentence, either works well.

Rester means to remain / to stay, while être just means to be.

So:

• l’argile est souple = the clay is soft
• l’argile reste souple = the clay remains soft / stays soft

Using reste emphasizes that the clay continues to be in that state, which fits the idea of as long as.

Here souple means something like:

• soft
• pliable
• flexible
• workable

With clay, souple suggests it is still easy to shape and has not hardened.

So reste souple is more precise than just is soft. It means the clay is still soft enough to work with.

In this sentence, on means we.

So:

• on continue = we continue

In modern spoken and everyday written French, on is very commonly used instead of nous.

Compare:

• nous continuons = more formal or careful
• on continue = very natural, everyday French

So although on can literally mean one, very often it simply means we.

Because on takes a third-person singular verb form.

So even when on means we, the verb is conjugated like il/elle/on:

• je continue
• tu continues
• il/elle/on continue
• nous continuons

That is why it is:

• on continue

not:

• on continues

Argile is a feminine singular noun:

• l’argile = the clay

It is written l’ because argile begins with a vowel sound, so la argile becomes l’argile.

You could think of the full form as:

• la argile → l’argile

though in real French, you would only use l’argile.

Good question. Since argile is feminine, the adjective should agree with it. It does agree here, but souple happens to have the same form in the masculine and feminine singular.

So:

• un matériau souple
• une argile souple

Both use souple.

Agreement still exists, but you just cannot see a change in spelling here.

You do see a visible change in the plural:

• des matériaux souples
• des argiles souples

Because du moment que here introduces a real condition or situation, not a feeling, doubt, wish, or uncertainty that would normally trigger the subjunctive.

So French uses the indicative:

• l’argile reste souple

This is the normal pattern in a sentence like this.

For a learner, the practical rule is:

• after du moment que meaning as long as / since / given that, you will usually see the indicative

Yes:

• Du moment que l’argile reste souple, nous continuons.

That is grammatically correct and means the same thing.

But in everyday French, especially in speech, native speakers very often prefer:

• on continue

instead of:

• nous continuons

So the original sentence sounds natural and idiomatic.

The structure is:

• Du moment que
  • clause
• main clause

So:

• Du moment que l’argile reste souple,
  on continue.

In English terms:

• As long as the clay remains soft,
  we continue.

The first clause gives the condition. The second clause gives the result or main action.

You could also reverse the order:

• On continue du moment que l’argile reste souple.

But the original order is very natural because it presents the condition first.

L’argile is pronounced approximately like:

• lar-zheel

More carefully, in IPA:

• /laʁ.ʒil/

A few points:

• the l’ is pronounced like l
• the r is the French throat r
• g before i sounds like the s in measure or the g in genre
• the final e is silent

So it does not sound like English argyle.

The comma is very normal here because the sentence begins with a subordinate clause:

• Du moment que l’argile reste souple, on continue.

It helps separate:

1. the condition
2. the main statement

In short sentences, punctuation can sometimes vary, but the comma is standard and helpful here.