While you can make your lye solution with brewed tea, many soap makers like to use ground tea leaves in their soap instead, either as an additive or as a natural colorant. It's easy to just add a few tablespoons of the dried botanicals into the soap as it comes to trace, but while the idea works well in theory, in practice, the results leave a lot to be desired.
Botanical Bleed in Homemade Soap
When you brew a cup of tea, the oils and essence of the botanicals—the tea leaves, herbs, spices, and flower petals—seep into the water, giving it flavor, scent, and color.
The same thing happens when you add botanicals to soap as it comes to trace. While it depends on the botanicals you're using, they're likely to impart a dull color on your batch of soap, and there's also sometimes a halo effect with the bits of botanicals bleeding into the soap as it sets. That said, not every botanical has a bleeding effect in homemade soap. Mints produce the most bleed, but lavender and chamomile will only cause slight discoloration.
Botanical bleed may or may not be a problem for you—if you're making soap for your own use, the discoloration might not matter. When you're making a batch of soap to sell or to give as gifts, you're likely to be more concerned about how it looks. Luckily, there's a simple solution to this problem.
Preventing Botanical Bleed
In order to prevent botanicals from bleeding into your batch of soap, you can steep them in hot water first, just as you would if you were making a cup of tea. Unlike with the tea you'd brew for yourself to drink, you'll leave the botanicals in the water until it cools completely.
Place the botanicals in a cheesecloth tied with a piece of string. Steep them in the hot water. Once the water is cool, remove the cloth with the herbs and squeeze it well until you've gotten all of the liquid out. Now, the botanicals can be added to your batch of soap at trace without causing discoloration and bleeding.
When to Steep Botanicals
By steeping botanicals before adding them to the soap, you're also removing many of the benefits for the skin, which come from their oils and essences. Sometimes this matters, while other times, it doesn't.
If you're adding herbs and tea to your soap for a visual effect or as a light exfoliant, steeping the botanicals first has no ill-effect on the quality of your soap—it will look just as good and exfoliate just as well. In these cases, it makes sense to steep the leaves first before adding them to the soap at trace.
If, on the other hand, you want to add botanicals for their healing effects—lavender or chamomile to soothe irritated skin, for example—then it's best to add them without steeping first and simply accept that there may be some discoloration.