Laundry prewashes are a shadow of what they used to be. Many years ago we had Preen (The Great Unstainer) and it worked very well. The reason for this was its mechanism of operation. It was essentially a dry cleaner in a can. In other words, it was solvent based and worked on the principle of dissolving oil and grease based stains, which then washed out. modern pre washes do not work nearly as well.
In fact there aren’t any prewashes on the market that use degreasing as their mechanism. Instead of this, they use things like Enzymes and Oxidizers. Now these work very well as spot cleaners, but they are not laundry prewashes. The concept of a laundry prewash is that you spray it on the stain before the garment goes in the wash. in other words, the prewash needed the washing cycle to be washed out. if the clothes didn’t go into the washing machine, the prewash would remain in the garment and the stain would not be removed. With enzyme and oxidizer based products, however, these don’t work nearly as well simply because the mechanism of these two processes is very slow. In other words they remove the stains on their own and do not need the washing machine to work. But the problem is as soon as these prewashes go into the washing machine their mechanism stops because they are washed away by the water in the washing machine. That’s why the older type degreasers worked very well.
So what do we do about it? Well, we can make our own laundry pre-wash using a degreaser. Now there are two types of these – solvent based and water based. They are easy to pick because the solvent based products are in aerosol cans and the water based products are not. But having said that, they don’t all work as well as each other. But you do have to buy them from automotive shops. That’s the only place that sells them. So go into an automotive shop find the degreasers and you are looking for the term “alkaline salts” (normally about 50g/L) on the label somewhere. This means they contain silicates, which are spectacularly good degreasers and therefore laundry prewashes. One brand I have used which works very well is Kenco but there are others.
So go into Bunnings, get yourself a generic spray bottle, put your degreaser in there and use it as a prewash. I did a test a while ago with one of these against a standard suite of stains; dirt, blood, shoe polish, oil, sump oil, ink, lipstick, red wine, grass and the automotive degreaser outperformed all of the so-called laundry pre washes available at the moment.