Гидратация теста выросла вплоть до того, что пекарский скребок использовали постоянно.

Because гидратация теста means the hydration of the dough.

In Russian, a noun often takes a dependent noun in the genitive to express of-relationships:

• гидратация теста = hydration of dough
• цвет хлеба = color of the bread
• вкус супа = taste of the soup

So тесто becomes теста because it depends on гидратация.

Because the subject is гидратация, and гидратация is a feminine singular noun.

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

• masculine: вырос
• feminine: выросла
• neuter: выросло
• plural: выросли

So:

• Гидратация выросла = The hydration increased

Even though теста is nearby, it is not the subject. It is just the dependent noun in гидратация теста.

This is a set expression meaning something like:

• to the point that
• so far that
• to such an extent that

So the sentence structure is:

• Гидратация теста выросла вплоть до того, что...
• The dough hydration increased to the point that...

This expression introduces a consequence of what happened before it.

A simpler near-equivalent would be:

• настолько..., что... = so..., that...

For example:

• Гидратация теста выросла настолько, что...

That would be very natural too.

By itself, вплоть often gives the idea of right up to, as far as, or even up to.

Common patterns include:

• вплоть до пятницы = right up to Friday
• вплоть до мелочей = down to the smallest details
• вплоть до того, что... = to the point that...

In your sentence, it is not really functioning as a fully separate word you would translate alone. It is best learned as part of the whole expression:

• вплоть до того, что

This is a very common Russian pattern: 3rd person plural with no explicit subject.

It often means:

• they used
• people used
• one used
• or, in natural English, a passive-like idea: was used

So:

• пекарский скребок использовали постоянно

literally is something like:

• they used the baker’s scraper constantly

But in smoother English, that often becomes:

• the baker’s scraper was used constantly

Russian uses this indefinite-personal construction very naturally when the specific doer is not important.

The verb here is использовать, and использовали is the past plural imperfective form.

The imperfective is used because the meaning is repeated, habitual, or ongoing:

• использовали постоянно = used constantly / kept using

This matches the adverb постоянно very well.

If you used a perfective verb, it would sound more like a completed single action, which would not fit as naturally here.

So the aspectual contrast is roughly:

• использовали постоянно = they were using it constantly / used it regularly
• a perfective form would suggest one completed use, which is not the point here

Yes, it is understandable and fairly natural in a baking context.

• пекарский = baker’s / baking-related
• скребок = scraper

So пекарский скребок means a baker’s scraper, often what English speakers call a:

• bench scraper
• dough scraper
• baker’s scraper

Depending on context, Russian speakers might also say more specific things such as:

• скребок для теста = scraper for dough
• пекарский шпатель in some contexts

But пекарский скребок is perfectly understandable.

Yes, Russian word order is flexible.

The sentence as written:

• Гидратация теста выросла вплоть до того, что пекарский скребок использовали постоянно.

puts the main development first, then gives the consequence.

You could rearrange parts for emphasis, for example:

• Вплоть до того, что пекарский скребок использовали постоянно, выросла гидратация теста.

But that sounds much less neutral and more stylistically marked.

The original order is the most straightforward:

1. state what changed
2. add the result

That is why it feels natural.

Yes. For example:

• ...что пекарский скребок использовался постоянно.

That would mean:

• ...that the baker’s scraper was used constantly.

So what is the difference?

• использовали = indefinite-personal; very common, lively, natural
• использовался = passive/reflexive; also correct, sometimes slightly more formal or heavier in style

Russian often prefers the active plural with an unspecified subject instead of a passive construction, especially in everyday or practical writing.

Yes, it is a real Russian word, and it is especially common in technical, scientific, and baking contexts.

In baking, гидратация теста refers to the ratio of water to flour in dough. So for people interested in bread-making, this is normal specialist vocabulary.

A more general learner might not know it, because outside those contexts it is less everyday than many common food words.

So:

• grammatically normal Russian
• semantically somewhat technical/specialized

Постоянно means:

• constantly
• all the time
• regularly, depending on context

Here it suggests frequent or near-continuous use because the dough was so wet/sticky that the scraper kept being needed.

It is stronger than something like:

• часто = often

So:

• использовали часто = used often
• использовали постоянно = used constantly / kept using

Yes, that is a good thing to notice.

Russian до того can mean different things depending on context:

1. before that

   • До того я этого не знал.
   • Before that, I didn’t know it.

2. as part of an intensifying structure such as:

   • до того, что...
   • вплоть до того, что...
   • meaning to the point that...

In your sentence, because of вплоть до того, что, it is clearly the second meaning. You should understand it as one fixed expression, not as a time phrase.