I’ve done a number of tests with different brands of clay. I’ve also used different brands to make various things. Through that process, Cernit Number One has clearly become my favorite brand. I will occasionally use another brand, depending upon what I’m making, because each has unique properties.
It’s important to note that Cernit Number One is very different from Cernit translucent and metallic which are usually softer and stickier.
Pros of Cernit Number One:
• It’s not sticky. Unless it’s really fresh, it normally has a fairly dry surface.
• It’s not soft or wobbly. A raw cut out shape doesn’t stretch or distort if you pick it up and move it. https://polymerclayjourney.com/2018/01/17/polymer-clay-firmness-test/
• It’s firmer than Premo, but not as hard as Kato, when raw or baked.
• I’ve never had to leach it.
• You don’t have to bake it an hour to make it strong. Thirty minutes is sufficient.
• It rarely breaks and it’s difficult to break.
• Veneers and sheets bake perfectly flat with no warping.
• It doesn’t shrink like other brands. https://polymerclayjourney.com/2018/01/17/polymer-clay-firmness-test/
• It has a nice satin finish when baked that’s not as plastic-looking.
• It has much less tendency for bubbles to magically appear during baking.
• It doesn’t become slimy in contact with water.
• The white and translucent don’t turn yellow when baked. https://polymerclayjourney.com/2017/02/02/baking-polymer-clay-multiple-times/
• Paints don’t scratch off of it after baking, such as Genesis heat-set oils, tinted liquid clays and most brands of acrylic paints. https://polymerclayjourney.com/2017/02/04/paints-on-baked-polymer-clay/
• It has almost no odor when raw or while baking.
• The translucent is very translucent—second only to Pardo. https://polymerclayjourney.com/2016/12/21/how-to-avoid-plaquing-in-polymer-clay/
• The metallics use a different type of mica powder which is more sparkly.
Cons of Cernit Number One:
• You may have to apply a little diluent to glass or other surfaces to get the clay to stick to it.
• Almost all colors darken slightly when baked, so you may need to compensate for this. https://polymerclayjourney.com/2017/02/15/polymer-clay-colors-when-baked/
• It becomes unconditioned fairly quickly. I mix Pardo Jewellery Clay into it for things I don’t plan to use right away, such as canes and veneers.
• If you want to bend or mold it, you need to either move it slowly and warm it up or mix in something to make it more pliable like Pardo Jewellery Clay, diluent or liquid clay. If you don’t, it will crack.
• You have to order it online because it’s rarely found in craft stores.
If you haven’t tried Cernit Number One, keep an open mind and give it a shot. I think you’ll be very glad you did.