Various mordants affect dye, and to a lesser degree, stain colors.  As a general rule the following is true:

• All aluminum salts will brighten the color and affect it the least, however they may affect pH.

• Copper salts will tint your colors with green/blue.

• Iron salts will tint your colors brown.

• Tannic acids will tint your colors brown & tan.

pH will change natural colors significantly, including pH of your water sources. For reliable and repeatable results use water with a natural pH. Most municipal waters will be neutral (pH 7).  Well water, pond, lake, and reservoir water will not nessicarly have a neutral pH.

Nutrients taken up by a plant affect the color compounds it holds.  These nutrients can vary by location, time of year, and even year to year based on gowning conditions. The same color source may yield slightly different amounts of color from season to season, location to location, and/or year to year.

pH will change natural colors significantly. Stains will be far more affected by pH changes than dyes. Please see About Natural Dyes, Stains, & Pigments for more information. 

Easy alterations to pH can be achieved with lemon juice and baking soda.

Many dyes take time to release from the dye source and attach to your material. How long you cook a dye in your pot will change how much color you get from it.  How long you cook your material in the dye pot will also change the depth color you get.

Not all dyes like heat or water extraction. Some require certain kinds of processing and handling. Using the right recipe will affect the finished results.