Is it possible to use oil painting mediums with colored pencils? That’s what Lorraine is asking. Here’s her question.
I’ve read of several different solvents that are used with coloured pencils but are worried about the archival quality of some of them on paper. Which are archival? Also are different solvents used with oil-based and wax-based pencils?

There are a lot of oil painting mediums on the market today, and a lot of opinions about their usefulness with colored pencils.
So to keep this discussion on course, I’m tackling each of Lorraine’s questions in turn.
Oil Painting Mediums with Colored Pencils
Let’s break this up into two parts, because there are so many painting mediums available. First, those mediums that do work well with colored pencils, then those you should probably stay away from.
Oil Painting Mediums You can Use with Colored Pencils
The mediums used most by colored pencil artists and oil painters are the basic mediums. Turpentine and odorless mineral spirits.
Most artists opt for odorless mineral spirits whether they use oil paints or colored pencils because turpentine has such a strong odor. It’s simply not advisable for use by people with sensitivities, or if you have to work in small, enclosed spaces. Even with proper ventilation, the smell lingers in the air, and if you’ve used a lot of it to blend colored pencils, the smell can also cling to the paper.
But both turpentine and odorless mineral spirits are as archival with colored pencils as with oil paints. If you use them correctly, you should have no problems with fading color or deteriorating paper.
Don’t use ordinary paint thinner from the lumber yard or hardware store. Yes, it is the same basic solvent as artist quality solvents, but without the additional refining. Cheaper, yes. Archival? No.
Oil Painting Mediums You can’t Use with Colored Pencils
Some of the other oil painting mediums might not transition from oil painting to colored pencil work quite as well.
For example, my favorite oil paints are M. Graham Oils. M. Graham Oils uses walnut oil as the vehicle for their paints instead of linseed oil or safflower oil.
They also produce walnut oil and an alkyd/walnut oil blend for thinning oils. Both would probably blend colored pencil to some degree, but neither is archival because they discolor paper, and perhaps damage it in other ways.

None of the other oils commonly used with oil paints would be suitable, and for the same reasons.
Liquin is another popular oil painting medium. It’s a glazing medium. My guess is that Liquin might blend colored pencils, but also would not be archival for use with colored pencils.
So my advice is to stick with the basics, and forget the more modern, specialty oil painting mediums when you use colored pencils.
Different Mediums with Oil-Based and Wax-Based Pencils
All colored pencils are made with a binder that allows the pigment to be rolled into pencil shapes. All binders contain some wax and some oil.
Wax-based colored pencils contain more wax than oil. They are usually softer, often slightly thicker, and put color onto the paper more easily.
Oil-based colored pencils contain more wax than oil. They are usually harder, often slightly thinner, and put color on the paper a little less easily.
Turpentine and odorless mineral spirits work equally well with both. You may need to adjust the amount of solvent you use with one type of pencil over the other, but you can use the same solvent for both.
Conclusion
I hope that information helps you, Lorraine.
A lot of natural and synthetic mediums are available for oil painters. Since turpentine and odorless mineral spirits are archival with colored pencils, it seems to make sense that all the other mediums are, too.
A good rule of thumb to remember is that if the medium contains any kind of oil or varnish, it’s probably not going to work well either with colored pencils or paper.
And if you decide to try one of them, don’t try it on a drawing. Test it first on scrap paper!