Soap Batch 1: Bastille Cedarwood & Eucalyptus Bar Soap

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First Batch Guide — Cold Process Method

Mold: Brambleberry 10" Silicone Loaf (10" L x 3.375" W x 2.5" H) Yield: 8–10 bars | Cure time: 4–6 weeks | Active time: ~1 hour

Safety First

  • Always wear safety glasses and rubber gloves before handling lye
  • Lye (sodium hydroxide) is caustic — it will burn skin and eyes on contact
  • Always add lye to water, never water to lye
  • Work in a well-ventilated area — lye fumes dissipate quickly but are harsh
  • Designate all soap equipment as soap-only — never return to kitchen use

Recipe

ComponentAmountNotes
Olive oil648gAny grade
Coconut oil, refined 76°162gRefined, not virgin
Castor oil90gBoosts lather volume and quality
Distilled water342gMust be distilled, not tap
Sodium hydroxide (lye)123g99%+ pure NaOH — Belle Chemical
Sodium lactate10ml (~2 tsp)Add to cooled lye solution; speeds unmolding
Cedarwood Virginian EO22gNOW Foods 1oz bottle
Eucalyptus EO5gPlant Therapy
Spent coffee grounds (optional)~35g (~2.5 tbsp)Medium-coarse grind (Encore setting 25-30); spread on paper towel and dry for a few hours before using

This recipe uses a 5% superfat (lye discount), meaning 5% of oils remain unsaponified intentionally. This adds skin feel and provides a safety buffer. Oil blend is 72% olive / 18% coconut / 10% castor. If you ever modify this recipe, always recalculate lye at SoapCalc.net — never eyeball lye quantities.

Instructions

Step 1 — Gear Up

Put on your safety glasses and gloves before touching anything. Set up your workspace with good ventilation. Lay out all equipment and pre-weigh all ingredients into separate containers before you begin.

Step 2 — Prep the Mold

No prep needed for the Brambleberry silicone loaf mold. Set it on a flat cutting board before pouring to prevent any sagging when full.

Step 3 — Make the Lye Solution

(Allow ~30 minutes to cool)

  1. Weigh 342g distilled water into your All-Clad 1.5qt bowl
  2. In a separate container, weigh 123g lye
  3. Slowly pour the lye into the water — never reverse this
  4. Stir until fully dissolved — solution will heat to ~185°F and release brief fumes; don't lean over it
  5. Add 10ml sodium lactate and stir in
  6. Set aside to cool to approximately 105–120°F

Step 4 — Prepare the Oils

  1. Gently melt 162g coconut oil — microwave in 20-second bursts or use a double boiler
  2. Combine with 648g olive oil and 90g castor oil in your All-Clad 3qt bowl — set aside a small splash (~15ml) of the olive oil in a separate cup for the kaolin clay slurry in step 6
  3. In a small cup, combine 22g cedarwood EO and 5g eucalyptus EO and set aside
  4. Check temperature — you want oils at roughly 105–120°F, within ~10°F of the lye solution before combining

Step 5 — Combine and Reach Trace

  1. Slowly pour the cooled lye solution into the oil bowl
  2. Stick blend in 5–10 second bursts, alternating with hand stirring
  3. You're aiming for "trace" — when the batter thickens to a light pudding consistency and drizzled batter leaves a trail on the surface
  4. With this oil blend, expect 3–8 minutes of blending

Step 6 — Add Clay, Fragrance, and Exfoliant

  1. Mix 18g kaolin clay into the small cup of reserved olive oil from step 4 until a smooth slurry forms, then stir into the batter
  2. Pour your pre-combined EO blend into the batter and hand stir for 1–2 minutes — do not stick blend after adding EOs, as this risks acceleration or overheating
  3. (Optional) Fold in ~35g dried spent coffee grounds and hand stir until evenly distributed — do not stick blend

Step 7 — Pour and Insulate

(Rest 24 hours)

  1. Pour batter into the mold on its cutting board; tap gently on the counter to release air bubbles
  2. Smooth the top with a spatula
  3. Cover with cardboard or a silicone mat, then wrap in a towel
  4. Leave undisturbed for 24 hours — this insulation helps the gel phase complete properly

Step 8 — Unmold and Cut

(Check at 24 hours; allow up to 48)

  1. Check firmness — soap should feel firm and not sticky
  2. If still soft, give it another 24 hours before unmolding
  3. Unmold onto parchment paper
  4. Slice into bars approximately 3cm thick using your Mac chef knife
  5. If bars crumble, they needed more time; if firm and fine-grained, you're set

Step 9 — Cure

(4–6 weeks minimum)

  1. Arrange bars on a rack with airflow on all sides
  2. Store in a cool, dry place out of direct sunlight
  3. Cure for a minimum of 4 weeks — 6–8 weeks is better for high-olive-oil bars
  4. Longer cure = harder, milder, longer-lasting bar
  5. Label bars with the batch date

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