Spills and spatters happen, regardless of how careful you are. It’s a lot easier to pre- pare for them than to wipe them out of your carpeting or off your wood floor later. All it takes is canvas drop cloths in your work area (a 4-ft. x 15-ft. cloth costs $15). The thick canvas stays in place, so you don’t need to tape it, and you can use it to cover any surface. Plastic drop cloths are slippery to walk on or set a ladder on and don’t stay in place. Even worse, paint spills on plastic stay wet, and they can end up on your shoes and get tracked through the house. Canvas is slippery on hard floors, so rosin paper ($10 for 400 sq. ft. at home centers) is better over vinyl, tile and hard- wood. Tape the sheets together and to the floor to provide a nonslip surface.

Back to the article. You can add water to all latex based paints / thinner to oil based paint. The tinting base has absolutely nothing to do with it. Say you are working outside and throughout the day you have to add a little water to keep the same consistency. If somebody really tried to add 20% to 50% water they no longer would be painting they'd be performing a whitewash or pickle finish. 

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