Make a paste of white vinegar and baking soda, thick enough so it will stick to where you want to clean, let it sit while you do something else( half an hour or so). You will find that the soap scum comes off quite easily.
I believe that if you use a mixture of baking soda AND white vinegar it will come clean w/o scrubbing. I've never actually cleaned (or even seen) an "acrylic" tub before, but I have used this solution on acrylic faucet handles to clean them of the soap/hand oil/dirt gunk.
I also use an "after" product; a polish and (albeit temporary) sealant called Gel Gloss. It comes as a spray or a pourable creme. It is in a hot pink can (white cap) w/blue & white lettering, and available @ Home Depot (and other of this type) stores.
For me, this is a "must have" product for keeping all kinds of surfaces polished/sealed between cleanings, especially those that come into contact w/water on a daily basis, such as sinks, tubs, etc. I wouldn't be w/o it in my business!
Avoid scratchy cleansers. I'd be leery of Comex or Ajax. The scratches will only encourage more gunk to stick and you'll have scratches. I use baking soda and water. It takes a little elbow grease at first, but it looks great and if you do it regularly, it doesn't take as long. And I don't poison the earth or my lungs when I do it. AND baking soda is very cheap. I just buy a fresh box to use in baking, and use the leftovers of the old box for cleaning.
Give it a good sprinkle with baking soda, dampen (well) a cloth or sponge with plain white vinegar and give it a scrub. Will take a little extra scrubbing the first time, but if you do this at least once a week it will keep your tub looking like new. Both of these products are environmentally friendly.
Get a bottle of Bathroom Cleaner Plus, it is sold by Amway, it will seem expensive but a very small amount goes a long way.
I have a chocolate brown tub and it keeps it clean and shiny
Clean it with a powdered cleanser such as Comet or Ajax, or use the Mr Clean magic eraser. A liquid cleanser such as Mr. Clean will also work, but the slight abrasive in the powder or the eraser will make the job a whole lot easier.
Wipe down your tub after using it to avoid this. I also have heard that using a liquid soap or shower gel will avoid this problem, but I use regular soap and so could not say for sure.
Everyone gets soap build up. You just have to clean your tub regularly.
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