How to Use a Corner Trowel for Clean Outside and Inside Corners

By Color Atelier Limewash Paint & Plaster | United States | Published: 2026-10-21

Category: How-to Guides

Learn the correct technique for using a corner trowel to achieve sharp, clean outside and inside corners when applying plaster or paint.

Quick answer

Use a corner trowel to finish both outside and inside corners by applying even pressure and working in smooth, continuous strokes to avoid digging into the surface.

Why a dedicated corner trowel matters

Standard flat trowels can leave uneven edges or gouge into the corner, especially on outside corners where the material builds up. A corner trowel's angled blade matches the corner geometry, letting you work both sides simultaneously without overworking the material.

Choosing the right corner trowel

A stainless steel blade resists rust and cleans easily, which matters when working with limewash or plaster that can harden quickly. The extra-small size of the Corner Trowel- Outside, Inside is ideal for tight corners and gives you better control than a larger tool.

Step-by-step guide

Prepare the corner and material: Apply a consistent amount of plaster or limewash to both sides of the corner using a flat trowel. Do not overload—excess material will squeeze out and create messy edges. Loading too much material is the most common cause of corner buildup and cleanup later.
Position the corner trowel: Hold the trowel so the blade sits flush against the corner line, with the handle angled slightly away from the surface. For an outside corner, the blade wraps around the edge; for an inside corner, it fits into the recess. Check that the blade is parallel to the corner before starting the stroke—misalignment causes uneven thickness.
Draw the trowel in one smooth motion: Pull the trowel upward or along the corner in a single continuous stroke, applying even, light pressure. Do not stop mid-stroke or rock the blade, which will leave a ridge or gouge. A jerky or halted motion is the main reason corners end up wavy or with visible tool marks.
Clean the blade and repeat: Wipe the blade clean after each pass with a damp cloth. For multiple coats, let the first coat set slightly before applying the next. Re-wet the blade if material starts to stick. Dried plaster on the blade will scratch the finish on the next pass.
Finish with a light touch: Once the corner is filled and smooth, make one final pass with a clean, dry corner trowel to remove any remaining ridges. Use minimal pressure—this is a burnishing step, not a material-moving step. Pressing too hard on the final pass can thin the corner and cause cracking as it dries.

Recommended tool

Corner Trowel- Outside, Inside: Stainless steel blade with anti-rust, easy-clean properties; soft-grip rubber handle for comfort and control. The stainless steel resists corrosion from wet plaster, and the rubber handle reduces hand fatigue during repeated corner passes.
Corner Trowel- Outside, Inside