Q: I recently installed a hydrocarbon drycleaning machine after using perc for more than 20 years. When garments had a stain that was both oil- and water-based (such as spaghetti sauce or salad dressing), we used to dryclean the garment first to remove the oil and then post-spot the remainder of the stain. For some reason, with the new hydrocarbon machine, after we post-spot the garment, there is still a yellow discoloration from the oil. Am I doing something wrong?
A: Since animal fats and vegetable oils readily oxidize with heat and moisture, it’s my opinion that this type of stain should always be pre-spotted — even in perc. Because perc is more aggressive on dry-side stains thanks to its higher KB value, it will remove grease, oil and wax more completely than hydrocarbons. Therefore, there’s less of a chance of leaving an oil-based residue in the fabric.
To properly pre-spot a combination dry-/wet-side stain, remove the dry-side component (grease or oil) with an oily-type paint remover (OTPR) or paint, oil and grease remover (POG), then flush the stain with volatile dry solvent (VDS). Treat the remaining stain on the wet side by first using a tannin procedure. If the stain remains, use a protein procedure.
In many cases, a bleaching agent such as peroxide must be used to remove the last traces of the stain.