How to properly clean a clinker facade?

Try it with vinegar or with cola.
Best to try it first on a spot that is not very visible.
So first wet the clinker and then rinse thoroughly.
You might also try it with heavily diluted hydrochloric acid. But be careful because of the efflorescences.
Choose a small spot where you still need to fill anyway.

Try it with vinegar or with cola. Best to start at a spot that is not very visible. So first moisten the clinker and then rinse well. You might also try with heavily diluted hydrochloric acid. But be careful because of the efflorescence. Choose a small spot where you will have to fill in anyway.

Vinegar, hydrochloric acid? As you already said, efflorescence is inevitable. 100 years ago, this was commonly done with hard-burnt clinker bricks. Whoever does this today needs a lot of courage.