Careful the drain cleaner stuff is quite diluted. Go to a motor factor and ask for motorcycle top up acid. You can get it 1 litre bottles for a couple of quid. If you want more take a friend as they sometimes limit you to 1 per customer. i have 6 litres sat on my kitchen floor waiting for me to finish something worth anodising? caustic soda you can ask the local shop to get you some on their next trip to the cash and carry (do that part outside for god sake,,,fumes, fumes, fumes). Dylon dyes work better than the others (not the one you put in the washing machine). Hope this helps