If you don’t have much experience working with water-based or oil-based clay, you might be tempted to mix materials trying to find the right consistency or workflow. Before you do, read this article—it might save you some serious headaches.

Mixing Scenarios

Have you ever found yourself working with oil-based clay that’s too hard to sculpt, thinking “I’ll use something softer on the surface to make my life easier”? Or perhaps you’re using water-based clay and decide to mix it with another type to achieve the right texture or color?

Think twice before doing this. There are solid reasons why you shouldn’t make this a general practice—or if you do, you need to learn the proper when and why to avoid problems down the road.

I recently had a student who covered his entire sculpture with a different plasticine grade because he thought his original choice was too hard. Halfway through the piece, with all the work already sketched out, he swapped materials and covered everything like a skin.

Another student working with water-based clay decided to use two different types on her piece as part of the design, hoping for more visual interest. At first glance, everything looked fine. But there are important reasons to be careful with this approach.

Mixing Water-Based Clays

It’s not that you can’t use different grades of plasticine or different water-based clays in the same work—it’s how you use them that makes the difference.

When working with water-based clay, consider what you’ll do with your finished piece:

If you’re planning to fire it: You must use clays that fire at the same temperature (or the same cone number, as potters say). Using clays with different firing temperatures can cause your work to weaken or break in the kiln—it likely won’t survive the process.

If you’re making a mold: You’re safe to mix different water-based clays since the piece won’t go through firing. You’re only sculpting to create a mold at the end.

Mixing Oil-Based Clays 

Oil-based clay behaves differently. Even if you’re planning to make a mold (so the work doesn’t need to last indefinitely), you still need to understand how to use different grades properly. The good news? It’s actually quite simple.

Use harder clay for highly detailed areas. Parts with fine details might need harder clay so you can carve without fearing easy damage. For example:

• Fingers: If your clay is too soft, fingers bend or get squeezed the moment you touch them
• Facial features: Soft clay won’t stay where you place it, and surfaces blur immediately when you try to smooth them

For these areas, harder clay provides the control you need.

Avoid mixing oil-based clay grades together in the same surface. When you smooth the surface, softer clay requires less work to get even, while harder clay needs more effort to reach the same level. If you have a surface with two different grades, hard clay areas remain uneven and require aggressive smoothing. If you work hard enough to even the hard areas, you’ll wash away the soft areas, this creates a nightmare scenario across your entire surface

Setting Up to avoid problems

In sculpture, since we use many resources and invest significant time, avoiding technical problems as much as possible so you can focus on your work instead of troubleshooting, is the best thing you can do. Here’s a simple checklist before you start:

Environment: Set up your workspace properly (not the living room unless you’re ready for dust and clay bits in the carpet). Make sure you have there right light conditions, enough space and you can remove dust or clay bits with no problem once you finish.

Armature: Ensure it’s strong and steady so it won’t cause problems later. This is a common mistake people have, making a quick armature thinking that will be enough for the job. If the armature don’t hold the sculpture steady while you are working and moves too much, this can bee I BIG PROBLEM down the road. My advice is, make sure it is strong and steady so you don’t have to deal with it later on. I have seen many students having to open up the sculpture to fix armature issues when they are pretty much ready to start detailing the work. That is very annoying!

Materials & Tools: Use the right material for your project and have the appropriate tools ready. The more experience you have the better you understand what you need for the work, so if you are a beginner, start with the basic tools and clay. From there you wind your way.

As you can see, there’s not much to keep in mind, but following these guidelines makes a significant difference in your experience.

Related articles: Check out “Where to Start if You’re a Complete Beginner” or “Defining the Surface in Clay – Sculpting Tips.“

Want more articles like this? Sign up for our newsletter and get early bird discounts on courses and workshops delivered straight to your inbox.