I was asked to help improve this sentence:

A flask filled with a green liquid was visible at the center of the table captivating Clayton’s full attention.

I’m unsure if the past participle phrase (or adjective) is nonrestrictive. If it isn’t, then it sort of sounds confusing without commas, as it seems to the reader that it is a past simple verb, which it is not.

Also, I recently learned that if a ing prhase is preceded by a comma, then it ALWAYS modifies the subject. This was a rule I learned from an english teacher on youtube, believe it or not!

So, I said to add a comma before the ing phrase.

But then I also decided to make captivating the main verb in the sentence, as this is more important to the idea of the sentence than the linking verb. Here is what I got:

Visible at the centre of the table, a flask, filled with a green liquid, captivated Clayton.

But then I thought that the two modifiers prevent flow. So I thought of making it into passive voice, so that the modifiers come at the end of the sentence as a cumulative sentence, a preferred style:

Clayton was captivated by the flask that was filled with a green liquid and visible at the centre of the table.

Would you change it to passive for this reason? Or how would you write it?

Thanks.

A flask filled with a green liquid was visible at the center of the table captivating Clayton’s full attention.

Usually, when a noun is preceded by a and there is no other modifier, the phrase or clause following it would be restrictive. In this case, it is, since it tells us which flask.

Also, I recently learned that if a -ing phrase is preceded by a comma, then it ALWAYS modifies the subject. 

I think they mean introductory -ing phrases. I don’t think this would hold true otherwise.

Visible at the centre of the table, a flask, filled with a green liquid, captivated Clayton.

Not so good. Too many pauses.

Clayton was captivated by the flask that was filled with a green liquid and visible at the centre of the table.

Not so good, either.  Was Clayton captivated and visible? Sounds like it.

How about “At the center of the table, a flask filled with green liquid caught Clayton’s attention”? (You don’t captivate attention; you captivate people. And, of course, the flask is visible.)

Yeah, I agree about the words visible and capticating being unneccessary/incorrect here. But I didn’t want to change the person’s work too much.

Your sentence is very similar to my first one, except that I placed commas around what I thought to be a non-restrictive phrase (or I thought I should place commas around it because filled looked like a verb when read fast).

Thanks, again.

I am not finding it wrong in any way

I don’t think it was ever wrong. We were just trying to make it better.

Welcome to the forum.