When I got to LA, we went to the Graphaids art supply store, which did not have my usual brand of copal. Instead I purchased a bottle of Weber Archival Copal Painting Medium, thinking it would be essentially the same thing. Wrong! I wish I had thought to read a review of it before purchasing it, but I foolishly trusted the big letters on the front of the label.
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Weber's "copal" is horrible. My first clue that there might be a problem was the smell. It smelled suspiciously like turpentine, so I checked the fine print. Sure enough, the list of ingredients includes turpentine. I never use turpentine. I have difficulty tolerating the smell and I find it to be absolutely useless as a medium. However, since I had already purchased the Weber "copal" and because the label claimed that the product has all the good qualities of real copal and none of the bad, I figured I might as well try using it.
As far as I can tell, there is no difference between plain turpentine and Weber's Archival Copal Painting Medium. It made the paint watery and thin, the flow was terrible, I felt like I was almost pushing the paint across the canvas, the paint was drying up on my palette within minutes, and it seemed like I had to use three times as much paint as I would with my regular copal medium. After maybe half an hour, I gave up and went back to the house, declaring that we needed to go to a different art supply store.
This time we were more cautious. I double-checked what I normally used, then we called around to area art supply stores to find one that had it in stock. Walser's art supply had several bottles in stock, so we made a quick trip there, navigating around the holiday mall traffic. I had a nice (short) chat with the man working there about how the Weber "copal" is crap. He suggested I try Da Vinci copal, but I wasn't willing to experiment any further with my mediums right now. Maybe I'll try it when I'm back home. What I did purchase was my reliable Grumbacher's Copal Painting Medium.
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This is good stuff. Maybe the Da Vinci will prove superior, but I've always been delighted with Grumbacher's copal. The smell is much nicer than turpentine, the flow is beautiful, it reduces the amount of paint I need to use, and the final colors are gorgeous.