ɪnˈɪʃəli ɐ mˈɪkstʃɚɹ ʌv fˈoːɹɾi pɚsˈɛnt pˈɛtɹəl ænd sˈɪksti pɚsˈɛnt ɡˈæs ˈɔɪl wʌz jˈuːzd; ðɪs wʌz lˈeɪɾɚ ɹᵻplˈeɪst baɪ ɐn ɐdhˈiːsɪv dʒˈɛl ʌv tˈɑːɹ, lˈaɪm ænd pˈɛtɹəl nˈoʊn æz fˈaɪv bˈiː.
Initially a mixture of 40% petrol and 60% gas oil was used; this was later replaced by an adhesive gel of tar, lime and petrol known as 5B.