The concentration of the HCL is not that crucial-provided it is just HCL it will do fine.The more concentrated it is, the less you will need to use.
I bought several litres of HCl at 16% concentration from a place that supplies materials to the building trade; it is made for cleaning bricks and removing graffiti.
Using Vovins tek, 3 or 4 drops of this added to 600ml of warmed distilled water gets the pH down to 3-4; it works like a charm!
I am paranoid of my brain. It thinks all the time, even when I'm asleep. My thoughts assail me. Murderous lechers they are. Thought is the assassin of thought. Like a man stabbing himself with one hand while the other hand tries to stop the blade. Like an explosion that destroys the detonator. I am paranoid of my brain. It makes me unsettled and ill at ease. Makes me chase my tail, freezes my eyes and shuts me down. Watches me. Eats my head. It destroys me.