Skip to content
Field Notes

Laundry Detergent

soap detergent
laundry detergent castile washing-soda borax unprocessed
Mix 15 min
Yield 1 gallon (~64 loads)
Keeps 6–12 months
Storage sealed container
Notes Will gel as it cools — this is normal. Shake or stir before each use.

Ingredients

  • 1 cup liquid castile soap (unscented)
  • 1 cup washing soda (sodium carbonate) — NOT baking soda — see series page for DIY washing soda instructions
  • 1 cup borax — optional — skip for sensitive skin
  • 15 cups total (6 boiling + 9 room temperature) water
  • 20–30 drops herbal infusion or essential oil — optional — lavender is classic

Overview

This is your workhorse — the recipe you’ll use for most loads of laundry. The three active ingredients each do different things: castile soap lifts dirt and grease, washing soda softens water and cuts through grime, and borax deodorizes and brightens. Together they clean as well as commercial detergent at a fraction of the cost.

The detergent will gel into a thick, sometimes lumpy consistency as it cools. This is completely normal and doesn’t affect performance. Just shake or stir before use.

HE machines: This recipe is low-sudsing (castile soap produces far less foam than synthetic surfactants) and works well in high-efficiency washers. Use ¼ cup per load.

Instructions

  1. Boil 6 cups of water in a large pot or Dutch oven.

  2. Remove from heat. Add the washing soda and borax (if using). Stir until completely dissolved — this is important. Undissolved washing soda will leave gritty residue on clothes.

  3. Add 9 cups of room-temperature water and the castile soap. Stir to combine.

  4. Let cool for 10–15 minutes, then pour into your storage container(s) using a funnel. A gallon glass jar or a recycled detergent bottle works well.

  5. Add fragrance if desired and stir or shake gently.

  6. Wait 24 hours before using. The detergent will gel and turn white/opaque as it sets. Shake well before first use.

How to Use

  • Standard top-loader: ¼ to ½ cup per load
  • HE front-loader: ¼ cup per load
  • Heavily soiled loads: Use the Heavy-Duty Laundry Detergent recipe from this collection instead

Pour directly onto clothes rather than into the detergent dispenser, as the gel consistency can clog some dispensers.

Borax-Free Version

If you prefer to skip the borax (for sensitive skin, babies, or personal preference), replace it with an additional ½ cup of washing soda and ½ cup of baking soda. The cleaning power is slightly reduced but still very effective for everyday loads.

Tips

  • Don’t substitute baking soda for washing soda. They’re chemically different. Baking soda is sodium bicarbonate — milder and less effective as a detergent booster. You can make washing soda from baking soda (see the series landing page for instructions).
  • Add white vinegar to the rinse cycle (¼ cup in the fabric softener dispenser) for extra softness and to remove any soap residue.
  • If clothes come out stiff or with residue, your water may be very hard. Increase the washing soda by ½ cup.
  • Concentrated version: Use only 10–12 cups of water total for a thicker, more concentrated detergent. Use 2–3 tbsp per load instead of ¼ cup.

Cost Breakdown

  • Castile soap (1 cup from a 32 oz bottle): ~$4.50
  • Washing soda (1 cup): ~$0.40
  • Borax (1 cup): ~$0.50
  • Total per gallon: ~$5.40
  • Cost per load: ~$0.08

Compare that to commercial natural detergent at $0.25–0.35 per load.