Pour ⅓ cup (79 milliliters) of liquid dish detergent into a spray bottle. The dish detergent will cut through the oils and grease that make up your soap scum, making it easier to wipe away the stuck on grime. You can use any dish detergent that is formulated to cut through grease. If you use too much detergent in your cleaning solution, it will not ruin your cleaner; however, the cleaning solution will be harder to wash away.
Measure out 1 cup (237 milliliters) of white vinegar. In addition to attacking bacteria and mildew, white vinegar is great for clearing away soap scum and lime deposits. While the smell may be off-putting, it evaporates away once the vinegar dries. If the smell of the vinegar really bothers you, try adding a few drops of a pure essential oil, such as lemon or orange oil.
Heat your vinegar in the microwave. Set the timer for 1 minute to warm the vinegar. Warm vinegar is easier to mix than cool vinegar, so it will help you create a better cleaning solution. You don’t need to boil your vinegar. Depending on the strength of your microwave, you may want to warm your vinegar in 30 second intervals to make sure that it reaches a slightly warm temperature rather than getting too hot or not getting warm enough.
Add the vinegar to the spray bottle and mix. Blend the two ingredients using a swirling motion. Continue moving the bottle until they are completely blended. Avoid shaking the bottle because it will cause excessive sudsing. Your end result should be a slightly foamy substance that is lightly tinted the color of your detergent.
You can increase or decrease the quantity of cleaner that you prepare by adjusting the amount of the ingredients as long as you maintain the 3 to 1 ratio of white vinegar to detergent. If you’d prefer, there are several non-abrasive commercial options available that are safe for fiberglass. Check the label to make sure that the product does not contain abrasive cleaning agents or bleach.