Jonathan

I can only vouch for what i have seen and used, most of the drain cleaners claim to be concentrated but do come in different strengths. What you get from the motor factors is acid and not cleaner which contains other ingredients. The caustic soda i use is commercial grade and stripped all the paint off my 72 year old lathe no trouble at all. Preparation as with all jobs is the critical part and there is very little difference between anodising dye and clothing dye. The stuff you get from Ebay will not be from ICI? others report poor colouring from red in general. If it was a true commercial quality dye it would have the correct fixers for aluminium and the fading would be minimal. Give the dylon stuff a go you may be surprised? and make sure you have thoroughly neatralised the effects of the acid beforeadding the dye.