Usually you can buy a base in the store but the problem I have with them is they are loaded with so many chemicals. Avoiding fragrances and parabens is important when dealing with skin sensitivities.Given the trauma you are already putting your scalp through, reducing the exposure to these ingredients (since they are already found in your relaxer) is super important.
I decided to make my own base. So here are the ingredients:
Pure Petroleum Jelly: the foremost, best bet for creating a barrier between your scalp and the lye. I don't often use mineral oil or petro-based products in my hair or skin otherwise, but in this case you really should use it.
100% Raw Shea Butter: Anti-inflammatory and antioxidant rich. The fatty acids in shea help to form not only a thick, emollient cream, but also a rich barrier with healing properties.
Jamaican Black Castor Oil: Followers of the JBCO craze online already know this, but for those unaware--this is the holy grail of growth promoting oils. It is praised for being moisturising, thickening, and strengthening for the hair. I used this largely for its emollient properties.
Coconut Oil: Considered to be one of the most nourishing hair oils. Excellent ability to protect and strengthen the hair, but in this case useful for minimizing hair/skin damage and preventing dryness.
I made a small batch intended for 2 or 3 uses. The ratios you decide to use are entirely individual, but the most important thing is that the concentration is mostly petroleum based. Both the Vaseline and shea butter will help to keep your cream solid. All you need to do is melt the coconut oil and the shea butter (I opted for a few seconds in the microwave). Once both are melted (be careful because it can get hot) add the Vaseline and JBCO to the mix. Once lukewarm, I poured my mixture into an empty glass jar I had and stored in the fridge until solid.
To apply, I simply parted my hair focusing on applying it to my scalp and not the new growth.
So How Did it Hold Up?
Well, I still burned.
Given the circumstances though (tangles+cleanish scalp), I'm not surprised. Plus, I do use a regular-strength lye relaxer. That being said, it definitely was not as bad as the last relaxer. My scalp flaked less and healed much faster than it did the last go around.
I do recommend others try this if they want a more natural, gentle alternative to commercial bases and greases. If you are anti-petroleum than you can try beeswax instead, but I strongly recommend the Vaseline. It will wash off completely anyway and won't have a chance to cause build-up.
Let me know if it works for you!