A complete cleaning involves discarding all of the used bedding, not merely "spot cleaning" the dirty spots.  After removing the old bedding, wash the bottom and sides of the cage with soap and water, rinse thoroughly, then place fresh, new bedding in the cage. After washing with soap and water, you can use a 10% white vinegar and water solution (1 part vinegar to 9 parts water) as a rinse before drying the cage bottom.  Using the vinegar solution once a week (each time you fully clean the cage) may help eliminate odors and remove buildup that water can't.. Particularly if you have multiple guinea pigs in one cage, you should clean out parts of the cage daily in addition to the once-a-week deep cleaning.  To spot-clean, remove and discard any areas of soiled bedding at the end of the day. Most guinea pigs will use one part of their cage as a toilet area; cleaning the toilet area daily will help with odor and cleanliness. .  Spot cleaning will become easier if you can train your guinea pigs to use a litter box.  Identify the area that your guinea pigs tend to use as a toilet area. Then place a litter box made for small mammals in that corner of the cage.  Your guinea pigs will be more likely to use the litter box if you put it near their hay. Guinea pigs usually have a "kitchen" area where they eat and poop a lot. However, don't expect them to always use it; guinea pigs can't be perfectly litter trained like cats. If they change the area in which they use the toilet, try moving the litter box to the new area. Clean out the litter box every 1-3 days depending on how much it is used. Never place clumping cat litter in a guinea pig's litter box.  Guinea pig-safe bedding material is the most appropriate option. Cleaning sprays specifically formulated for small animal cages can help minimize cage odors.  Check your local pet store for products that are safe and effective for guinea pigs. Make sure you use only as much as the label recommends.  To use a cage-cleaning spray, remove all used bedding from the cage.  Spray the tray of the cage liberally with the cage cleaner. Allow the cage cleaner to soak into the cage for 3-5 minutes. Use a rough towel to wipe away cage cleaner and loosened debris from the bottom of the cage. Allow the cage to dry completely (in the sun if possible), place fresh bedding in the bottom of the cage, and return your guinea pigs to their home. You may want to continue using soap and water to clean the cage in addition to the cage cleaner. Bedding formulated to block odors, such as Carefresh, can keep the cage smelling fresh longer.  Place 1-3 inches of bedding in the bottom of your guinea pigs' cage.  Be sure to scoop out wet or soiled bedding daily.  Though odor-blocking bedding can make the guinea pigs’ cage smell better, you should still clean the cage well and completely replace the bedding at least once every week. Baking soda is marketed as odor-controlling, but it can cause irritation and should not be used.
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One-sentence summary -- Clean your guinea pig's cage at least once every week. Spot-clean your guinea pig's cage daily. Litter-train your guinea pigs Use a cage cleaning spray. Use odor control bedding.


Ideally, you should have at least two red clays, two yellow clays, one white clay, one translucent clay, and one black clay.  Try to include both one warm red clay (with a hint of orange) and one cool red clay (with a hint of violet). Likewise, grab one warm yellow clay (with a hint of orange) and one cool yellow clay (with a hint of green). Note that you can use more than two hues each of red and yellow, if desired, but using at least two should still allow you to observe the principle and understand how it works. Make three more samples by combining equal parts of one red and one yellow clay. Follow the same procedure used to make the first orange sample.  Warm red and cool yellow should create a medium-tone apricot color. Cool red and warm yellow should create a medium-tone melon color. Cool red and cool yellow should create a dull orange with hints of brown in it. Pick your favorite created hue of orange and duplicate the color twice more. You can lighten orange clay in two ways, and using two samples of the same hue will make it easier to compare results.  Add a small pinch of white clay to one orange sample, blending until no streaks remain. The color should have a lighter tint while also looking less bright. Add a small pinch of translucent clay to the other orange sample, blending until no streaks remain. The color should look less bright but should not change value or tint. Note that adding too much translucent clay will create a semi-transparent wash instead of an opaque orange. Create another sample of your favorite orange clay color. Pinch off a small piece of black clay and mix it into the sample, blending until no streaks remain.  The resulting orange will have the same hue, but the black should give it a darker shade. As a result, the orange may look slightly brown. Black clay can have a dramatic effect on other clay colors, including orange, so you should work in very small amounts to avoid darkening the shade too much.
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One-sentence summary --
Obtain several hues of clay. Work through the other red and yellow combinations. Lighten the orange. Darken the orange.