Combine warm water and vinegar in a spray bottle. Use equal quantities of both liquids and shake well to mix. The spray bottle will give you greater control over the application of the vinegar, which will be helpful when cleaning narrow spaces like grout lines. A spray bottle of vinegar is a convenient natural cleaning solution to have around in a pinch.

Sprinkle baking soda along one section of grout lines. You won’t need to use much—a thin dusting will be fine. Work the baking soda into the grout using your fingertips or the bristles of a brush. For maximum efficiency, proceed in small squares, following the grid-like pattern of the grout a few feet at a time. For particularly bad stains, you can also mix up a paste of baking soda and water, apply it to the grout and leave it to take effect overnight.

Spray the baking soda with the vinegar solution. Together, the two ingredients will start a mild chemical reaction, creating a fizzy foam that will bubble over the grout. Allow the baking soda and vinegar to sit for 5-10 minutes to ensure that it’s had time to eat away at the worst of the buildup.

This foaming action will make it much easier for the vinegar and baking soda combination to penetrate down into the tiny pores of the grout. To get the most out of the mixture’s stain-lifting power, wait until the foaming has died down before you begin scrubbing.

Scrub the grout clean. Using a stiff-bristled brush, scour the grout and space between the edges of the poly crystal tiles forcefully. After the vinegar and baking soda treatment, you should be able to lift out even the heaviest stains. Once you’re finished, give the floor a thorough rinse using a wet rag or sponge, then leave it to air dry.

Special brushes designed for cleaning grout can be bought cheap at all home improvement stores. Alternatively, you might also use a long-handled kitchen dish scrubber. Repurpose an old toothbrush and use it to clean grout. The narrow head of the brush coupled with the long handle make it the perfect tool for getting down into the spaces between wood tiles. Scrubbing grout by hand can be time-consuming, but it’s without a doubt the most effective means of restoring it to its original color.