You don't say if the negs are B&W or colour. Any organic solvent could be disastrous on colour negs.(posted 8903 days ago)Methylated spirit might be more economical, and a bit safer than lighter fuel. Old-timer press guys used to use it as a final bath when they were in a hurry, it adsorbs the water and evaporates quickly, giving dry negs in minutes. A few drops per litre of washing up detergent is totally harmless to negatives.