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Field Notes

Heavy-Duty Laundry Detergent

soap detergent
laundry detergent castile washing-soda borax heavy-duty unprocessed
Mix 15 min
Yield ½ gallon (~32 loads)
Keeps 6–12 months
Storage sealed container
Notes Concentrated — will be thicker than regular formula. Shake well before use.

Ingredients

  • 1 cup liquid castile soap (unscented)
  • 1½ cups washing soda (sodium carbonate)
  • 1½ cups borax
  • ½ cup baking soda — extra deodorizing power
  • 8 cups total (4 boiling + 4 room temperature) water
  • ¼ cup coarse salt — optional — helps as a water softener and scrubbing agent
  • 20–30 drops herbal infusion or essential oil — optional — tea tree or eucalyptus for antibacterial boost

Overview

This is the regular laundry detergent’s bigger sibling. More washing soda, more borax, less water — a concentrated formula designed for the loads that need extra help. Think muddy garden clothes, greasy shop rags, gym clothes that have been sitting in a bag for too long, and kids’ clothes that look like they’ve been used as napkins.

The higher concentration of washing soda and borax gives this formula significantly more degreasing and deodorizing power. The baking soda adds additional odor absorption, and the optional coarse salt acts as both a water softener and a mild abrasive during the wash cycle.

Instructions

  1. Boil 4 cups of water in a large pot.

  2. Remove from heat. Add the washing soda, borax, baking soda, and salt (if using). Stir until completely dissolved. The baking soda will fizz slightly — this is normal.

  3. Add 4 cups of room-temperature water and the castile soap. Stir to combine.

  4. Let cool, then pour into storage container(s).

  5. Add fragrance if desired.

  6. Wait 24 hours for the detergent to gel before using.

How to Use

Because this is a concentrated formula, you need less per load:

  • Standard top-loader: 2–3 tbsp per load
  • HE front-loader: 1–2 tbsp per load
  • Pre-soak for extremely soiled items: Add ¼ cup to a basin of hot water. Soak clothes for 1–2 hours before washing.

When to Use This vs. Regular Detergent

Use the regular detergent for everyday clothes, bedding, and normal laundry. Use this formula when you need extra cleaning power:

  • Work clothes (dirt, grease, oil)
  • Athletic gear and sweaty clothes
  • Cloth diapers
  • Muddy outdoor/garden clothes
  • Kitchen towels and rags
  • Anything with strong odors
  • Heavily stained items (pair with the Stain Pre-Treat from this collection)

Tips

  • Don’t use this on delicates. The high alkalinity from the extra washing soda can be harsh on silk, wool, and other delicate fabrics. Use the Delicate Detergent from this collection instead.
  • Pre-soak really works. For the worst loads, dissolve 2 tbsp of this detergent in a basin of hot water and soak the clothes for an hour before washing. Most stains and odors won’t survive that treatment.
  • Tea tree oil adds genuine antibacterial properties to the wash — useful for gym clothes and cloth diapers.
  • This gels thicker than the regular formula due to less water. If it’s too thick to pour, add a cup of water and shake.