The natural beauty of Slate River clay

June 2024

Karen Breukelman loves creating. From the physical wedging and throwing of the clay on the wheel to the glazing of her finished products, Karen is in her element. She loves to try new ideas and techniques so when her neighbour struck clay when he was digging his well, Karen jumped at the opportunity.  
Karen knew there was a history of quality clay coming from the Slate River Valley. The local quarry that supplied the clay for the Rosslyn Brickyard from 1976 to 1985 was just down the road from them. “I thought I would experiment and see if I could make pottery with this wild, local clay,” she says with a grin.

The beautiful grey/blue clay lays around fifteen feet below the surface and is free of silt, sand, rocks or roots. All Karen had to do was wedge it (knead it by hand to remove air bubbles and work it into a consistent clay body) and it was ready for the wheel. The clay threw on the pottery wheel like a dream due to its smooth and soft almost cream-cheese like consistency. Although the odd tiny stone worked its way through the clay, they only added character to the pots. 

When it was time to fire, the clay came out a gorgeous red brown colour with a hint of purple. Karen had never seen this unique colour before and admired the fact that the unglazed fired surface had a sheen to it, almost like it already had a clear glaze applied. She decided to leave portions of each pot unglazed, so the natural surface could be appreciated fully and give people a true glimpse into the character of the clay.

The challenges of using the clay surfaced when Karen had to figure out the proper firing temperature. When a potter purchases a commercial clay they know the recommended temperature, but with this clay, Karen had to find it out for herself. After a few failed attempts, she determined the perfect firing temperature was Cone 1, 2079°F.

Karen discovered that the clay also had a much higher shrink rate than most commercial clays. She had to make her pottery twenty percent larger than what she wanted the final pot to be. That meant if she wanted a cup to be 5 inches tall, she had to throw it on the wheel to about 6.5 inches in height. Because of the high shrink rate, the pots had to be dried very slowly and carefully under plastic for weeks to avoid cracking. Unfortunately, all the glazes she had for her higher firing clay didn’t work at this temperature either, so she had to start over and mix and purchase all new glazes for the clay. 

Her perseverance paid off. Her creations are not only unique but absolutely beautiful.

“I really enjoy using this clay on the wheel. I’ve enjoyed making mugs, vases and planters, but my favourite things to make are trees. I make many trees at Christmas every year and I’m really excited to share how beautiful the contrast of this dark clay looks with my new glazes.” 

You can follow Karen on Instagram @mbbpottery, check out her website at, or follow her greenhouse on Facebook.

If you want to get up close and personal with this truly local pottery, the Slate River Clay Collection will be available in Karen and her partner, Gerald’s, greenhouse this spring at MBB Greenhouse (My Blooming Business) at 341 Hanna Rd, Slate River.

Donna White is an accomplished author and Jubilee Medal winner for her volunteer work with World Vision. Visit her website at

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