This Help Center article is a summary of the official Earthaus Interior Sand & Stone Finishes application guide. Download the full Interior Sand & Stone Finishes Application Guide (PDF).
Overview
Sand and Stone Finishes are part of the Earthaus BUILD (pozzolanic hydraulic lime / PHL) plaster system for interior natural building wall systems. The materials are hydrated lime, pumice pozzolan, and carefully selected aggregates. This guide covers application of Sand and Stone Finishes over a PHL Binder brown coat. For application over drywall, refer to the standalone Sand and Stone installation guides instead.
Sand Finish: Apply 1/8" over a sponge-floated brown coat. Unsealed by default; may be sealed with Olive Oil Soap Sealer.
Stone Finish: Apply two wet-on-wet 1/32" finish coats over a 1/8" Sand Plaster base coat. Sealed by default with Olive Oil Soap Sealer.
Safety Precautions
Hydrated lime is strongly alkaline and can cause severe injury. Take these precautions when working with Sand and Stone plasters:
Wear eye protection, gloves, long sleeves, and pants.
Wear a particle mask/respirator.
Eyes: Flush immediately with copious cold water; seek immediate medical attention.
Skin: Wash with cold water, then mild soap; rinse with white vinegar if irritated; see a physician if irritation persists.
Inhalation: Move to fresh air; stay away from dust until symptoms subside.
Ingestion: Do not ingest; seek medical attention immediately.
Project Planning & Preparation
Substrate preparation:
The PHL Binder brown coat should be sponge-floated and lightly smoothed before applying finishes — smoothed enough that floating sand is embedded, but not over-smoothed (which compromises bond). A coarse, sandy brown coat may need to be scraped down or take extra Sand Plaster coats to cover.
Dampen the brown coat before finishing to control suction (darkened but no visible standing water).
Do not exceed 1/8" per coat — exceeding this risks shrinkage cracking.
Sand and Stone Finishes must not be used to fill or flatten uneven areas. To level a wall, build it out with additional PHL Binder coats instead (see the PHL Binder Application Guide, Brown Coat).
Working time & storage:
Mixed interior plasters may be stored for 14 days without adverse effect on bond strength.
Store below 60°F, tightly covered.
Mixing
Sand Plaster:
Add 8 quarts of water to a 5-gallon bucket.
Add the Mineral Pigment Pack and mix vigorously for 1 minute.
Strain the pigmented water through a 5-gallon paint strainer.
Add 1/3 bag of Sand Plaster and mix. Repeat until all powder is incorporated.
Mix vigorously for 3 minutes.
Stone Plaster:
Add 9 quarts of water to a 5-gallon bucket.
Add the Mineral Pigment Pack and mix vigorously for 1 minute.
Strain the pigmented water through a 5-gallon paint strainer.
Add 1/3 bag of Stone Plaster and mix. Repeat until all powder is incorporated.
Mix vigorously for 3 minutes.
Application
Sand Finish:
Apply Sand Plaster in an even 1/8" coat to a dampened brown coat.
At ~60% dry, smooth with a clean trowel (a light mist of water helps).
Optional: create texture while wet.
Allow to dry; the color lightens significantly when fully dry.
Optional: seal with Olive Oil Soap Sealer (see below).
Stone Finish:
Apply a 1/8" Sand base coat to the dampened brown coat; smooth at ~60% dry. Allow it to dry fully (it lightens significantly when dry).
Dampen the Sand base coat before applying Stone (darkened but no standing water).
Apply two Stone Finish coats wet-on-wet (each ~1/32", total max 1/16") — a first tight coat, then a "double back" second coat as the first firms.
Smooth with a clean trowel as the second coat firms. Do not over-trowel a too-firm surface ("burning" causes dark marks that are hard to remove).
Allow to dry; the color lightens significantly when fully dry. Stone Finish is sealed by default — see below.
Olive Oil Soap Sealing (Optional)
Apply only when the surface is completely dry.
Dilute 1 part Olive Oil Soap : 8 parts water.
Apply liberally from the bottom up; wipe excess with a clean cloth.
Customer Support
For product questions, email support@earthausplaster.com. For project-specific guidance, schedule an Earthaus technical consultation.
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