Truth Serum is a water recipe designed for tea analysis.
10x Concentrate – Do not drink!
- 3785.4g distilled water – Try a variety of brands to find one that is free of plastic/metallic notes.
- 0.345g sodium chloride (table salt)
- 1.672g sodium bicarbonate (baking soda)
- 0.773g magnesium chloride hexahydrate
- 0.154g magnesium sulfate heptahydrate (Epsom salt)
- 1.671g calcium sulfate dihydrate (gypsum)
Brew water – Do drink!
- 3406.9g distilled water
- 378.5g concentrate
- Silica – Optional. Add 1-3 drops per liter of brew water to enhance the mouthfeel. This is not officially a part of the recipe.
Tools – Not optional.
- Milligram scale – For the minerals.
- Higher capacity scale – For the water.
- TDS Meter – For verification and troubleshooting. TDS meters usually underreport by roughly one-third, but at least it will tell you if you’ve made an order of magnitude error.
- Squeeze bulb – Useful in various ways throughout the entire process.
- Silica desiccant packets – Throw one of these in the bag of magnesium chloride hexahydrate, which tends to deliquesce fairly quickly.
- Consumer-grade milligram scales tend to have unpredictable and inconsistent behavior. Get to know your scale and work around its behavior. Try to load the minerals into the dish (included with the milligram scale) in larger amounts. Loading the minerals only a few milligrams at a time tends to “confuse” the scale. Even small errors will have significant impacts in practice, so be exact. To ensure that the mineral dosage is correct, weigh the dish by itself before adding minerals and write that number down. When it comes time to add the mineral, place the dish onto the scale and tare it. Add the mineral until you get the correct reading from the scale, then remove the dish and tare the scale again. Wait one minute for the pressure plate to return to its original position, then weigh the dish with the mineral in it again. The reading should be equal to the weight of the dish plus the target weight of the mineral. You will likely see an error upon following these steps, and that’s to be expected, just add or remove some mineral to get the correct reading. Take the time to be exact.
- Use the squeeze bulb to wash off any remaining mineral from the dish into the water. Some of these minerals tend to stick. Make sure that you’ve filled the squeeze bulb from the already-measured jug of 3785.4g distilled water, and empty any remaining water back into the mix when finished dosing the minerals.
- To avoid precipitation of minerals, wait several minutes after adding each mineral, shaking occasionally. If you notice any precipitate in the water, you’ll need to start over.
- Try aerating the water by pouring it into your kettle from a height before boiling it. This enhances the texture by reducing astringency and adding “vertical volume”. It also affects the flavor profile by reducing intensity. It is best to try the water with and without aeration to become familiar with the effect, and please remember that aeration is a spectrum. You may prefer a different level of aeration than I do. I prefer little to no aeration for most of my tea.
(Special thanks to Martin Lersch at Khymos for this incredibly useful tool.)
Where to begin? First, a clarification: Ratios are based on mmol/L numbers, which is the number of molecules rather than the mass of those molecules, which is measured in mg/L. I’m no chemist, but this concept seems integral to the design of the calculator, as well as to understanding water chemistry.
Going back to the screenshot, there’s a lot going on here, so I’ll speak on the 5 primary concepts I had in mind when creating the recipe. These summaries are greatly oversimplified, but they’ll do for this post.
- Ca:Mg ratio – Calcium (Ca) expresses sweetness. Magnesium (Mg) expresses pungency/tannins, intensifying the aftertaste in the process. The 2.15:1 ratio balances sweetness and pungency.
- Cl:SO4 ratio – Chloride expresses sweetness and smooths things out, reducing rinse taste, but also character/complexity. Sulfate (SO4) expresses astringency, bitterness, character/complexity, and rinse taste. It also extracts scum (debris). The 1.33:1 ratio results in a reasonable amount of sweetness and plenty of character.
- Na:K ratio – Sodium (Na) has a salty taste, though it isn’t really noticeable in the amount that’s used for this recipe. I didn’t like the effect of potassium (K) in my water, because even in minute amounts it presented as a cold, inedible bitterness. For that reason, I didn’t use any potassium in this recipe.
- H:A ratio – The extraction power of hardness (H) minerals is limited by alkalinity (A), which acts as a buffer. A too-high ratio of hardness to alkalinity will result in excess astringency and a generally intense/powerful extraction. A too-low ratio will result in dull, weak, and “blurry” tea. This ratio was pushed to the brink of excess astringency/intensity.
- Overall mineral concentration: Keeping all other factors constant, increasing the overall concentration will result in a thicker and stronger brew. When adjusting concentration, the H:A ratio should be adjusted to compensate for the change in intensity. The current concentration works well enough for most types of tea.
- This post will be updated from time to time to adjust the recipe and/or include new information.
- Truth Serum is not intended for general tea enjoyment. I recommend using Simple Syrup for that instead.