Kiln Shelf Conditioner & FREE Powder

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FREE Powder | Pro Tips | Tutorials | Product Warnings

What is Kiln Shelf Conditioner?

Kiln Shelf Conditioner by Jen-Ken Kilns is an ultra-refined, high-fire liquid kiln wash—milled twice for smooth application. It helps prevent glass and glazes from sticking to shelves, saggers, drapes, and molds, though occasional touch-ups may be needed if chipped. For glass firings, it's designed to be used in tandem with FREE powder on surfaces already coated with Kiln Shelf Conditioner. FREE powder forms a protective barrier between the glass and the surface to further prevent sticking.

Kiln Shelf Conditioner Instructions

Please read these instructions thoroughly before beginning.

STEP 1: Clean the Surface of the Shelf

Ensure the shelf surface is free of dust, debris, and residue. If any kiln wash remains, scrape and smooth it before continuing—we recommend using a 4” scraper. Then, wipe with a lightly damp sponge or cloth to remove remaining particles, but do not saturate the shelf with water. The surface should be fully dry—or just slightly damp—before applying the conditioner.

NOTE: Residual Kiln Wash

Most shelves with old kiln wash can be soaked in water to help remove the remaining materials—as long as they haven’t been used in high-fire firings, which can harden the wash and make it difficult to remove. Always ensure the shelf is completely dry before applying Kiln Shelf Conditioner.

STEP 2: Stir AND Shake

First, stir the Kiln Shelf Conditioner thoroughly. Then, shake the jar vigorously to fully combine the water layer on top with the settled clay at the bottom.

STEP 3: Apply a Thin Coat of Shelf Conditioner

Use a horsehair or dry mop brush to apply the Shelf Conditioner, brushing in a single direction until the entire shelf is evenly covered. Only apply thin coats—thicker layers can dry unevenly, leading to curling or peeling. If peeling occurs, scrape off the kiln wash and start over, applying thinner layers. A small amount of water can be added to thin the conditioner if it has thickened over time.

STEP 4: Let the Kiln Conditioner Dry Completely

Allow the Kiln Conditioner to dry fully before applying additional coats. Drying time may vary, but using a fan or placing the shelf in direct sunlight can help speed up the process. When it's ready, the surface will turn white.

STEP 5: Apply Remaining Coats

Continue applying thin, even coats, shaking or stirring the Conditioner before each one. Alternate brush direction with each layer (e.g., horizontal, then vertical) to ensure full and even coverage. Apply a total of 4–6 coats, or until the surface appears matte and opaque white with no visible bare spots.

STEP 6: Smooth Dried Layers (Optional)

Once all coats of Kiln Shelf Conditioner are fully dry, lightly buff the surface with fine sandpaper for a smoother finish.

STEP 7: Pre-Fire the Shelf

To ensure proper adhesion of the Kiln Shelf Conditioner, pre-fire the shelf or mold with a ramp rate of 250°F per hour up to 800°F. Allow the shelf to cool completely before applying FREE and using the kiln.

NEXT STEP: Apply FREE Powder (Glasswork Only)

See directions below for best results.

FREE Powder

FREE is a finely milled powder designed to be used on kiln shelves and molds that have already been pre-fired with Kiln Shelf Conditioner. It forms a delicate barrier between the glass and the shelf surface, allowing the glass to shift slightly during firing. This movement helps release trapped air and gases, reducing the chance of bubbles forming underneath the glass—especially in full-fuse or large panel projects.

FREE Powder Instructions

STEP 1: Prepare the Surface

Ensure your kiln shelf or mold has been fully coated with Kiln Shelf Conditioner and pre-fired. The surface should appear matte and opaque white with no bare spots. This provides the proper foundation for FREE to do its job effectively.

STEP 2: Pour FREE into a Sock

For a smooth and even application, pour the FREE powder into a clean sock, stocking, or other breathable fabric. This creates a simple and effective powder puffer that allows for better control and helps reduce mess or excess dust. Knot the open end of the sock to keep powder secure.

STEP 3: Apply with Gentle Blotting

Hold the sock and gently blot it across the surface of the shelf or mold. Do not rub, shake, or squeeze the sock—just tap lightly to allow the powder to pass through the fabric in a soft, even layer.

Avoid creating airborne dust. Do not blow or brush the powder across the surface. Gentle blotting is all that’s needed.

STEP 4: Check for Coverage

Inspect the shelf surface after application. Your goal is a thin, even layer that looks lightly frosted—not heavily coated or clumpy.

Too much FREE can interfere with the surface finish or cause uneven results during firing.

Need Help?

Not sure if you've applied it correctly? Email us a photo—we're happy to take a look and guide you!

💡 Pro Tips

Dealing with Bristles on the Shelf

If you notice bristles on the shelf after applying the Conditioner, avoid wiping them off while the Conditioner is still wet, as this may leave marks and require you to start over. Once the Conditioner is completely dry, gently rub the surface with your fingers in small circular motions over the bristles to remove them. Do not apply pressure. If the bristles are fine, you can leave them in place—they will burn off during firing without leaving a mark.

Small Scratches & Dents

For small scratches or dents on the shelf surface, start by puddling the Shelf Conditioner into those areas to fill them in before applying additional layers.

Removing Glass Pieces

Use a suction cup (even a toy dart works great!) to remove glass pieces after firing and prevent damage to the kiln shelf.

Avoid Scraping the Shelf

Using your fingernail or other tools to remove stuck pieces can dig into the smooth layer of Shelf Conditioner and cause issues with future firings.

🎥 Video Tutorials

Coming soon!

Our video guides will make it even easier to get started with Kiln Shelf Conditioner and FREE powder.

Product Warnings

External Use Only

Do not ingest. These products are intended for external use only.

Avoid Skin Contact

Minimize skin contact; wash hands thoroughly after handling.

Keep Away from Kiln Elements

Do not allow the Kiln Wash Conditioner to come into contact with kiln elements or sidewalls, as this may cause damage.

Do Not Freeze

Store in a dry, temperature-controlled area. Freezing may alter the product’s performance and consistency.
If you're placing an order during cold weather, be mindful of your local temperatures.

If there's a chance your shipment will be left outside, make arrangements to be home or have someone receive it. Extended exposure to freezing conditions—such as being left on a porch or in a mailbox—can affect the quality of the product.

Use Caution When Sanding or Scraping

If dust is generated while sanding or scraping shelves or applying FREE powder, wear a mask and work in a well-ventilated area.

Crystalline Silica Warning

Contains <0.1–1.0% crystalline silica, a substance known to the State of California to cause cancer.

For more information, visit P65Warnings.ca.gov.

Material Safety Data Sheet

A full MSDS will be available soon. Check back for detailed safety and handling information.

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