I have been using alcohol inks for a couple of years, but I'm too cheap to buy the official Ranger Blending Solution (since it costs $6-8 for a 2 oz. bottle), so I have been using regular Rubbing Alcohol (70% alcohol) forever. I bought two 32 oz. containers at Costco (I think for about $6) and they have lasted me forever. I kept reading on alcohol ink tutorials that the 90% alcohol was the stuff to buy as a substitute for the blending solution, but whenever I looked for it, the store didn't carry it (most drugstores have it, but I never remembered to look at the drugstore). So, low and behold, I was at Target picking up the weekly necessities, and I glanced in the direction of the rubbing alcohol on the bottom shelf, and they had 90% alcohol rubbing alcohol. So for about $3 for a 32 oz container, it cost the same as the stuff I bought in bulk. So I thought I better compare the two and see if one is really better than the other.
I grabbed two white ceramic tiles that had the same finish. I didn't have any glossy ones, so these with a satin finish did the trick. I put a single large drop of Bottle Green on each tile and then used an eyedropper to drop a large drop of each alcohol onto the green to see how they reacted.
As you can see in the photos, they both reacted with the ink, but the 90% alcohol reacted a bit more.
Next I tested to see if the alcohol had a different effect on stamped ink. I loaded my applicator with three small drops of Twilight Purple on each side. I then dropped alcohol onto each purple drop. I used 90% alcohol on the left side and 70% on the right side. I stamped three rows onto the tile and noticed little to no difference in the way the ink behaved when thinned with 70% versus 90%.
I layered some Sailboat Blue thinned with more alcohol over top to create this pretty watercolor-look tile.
Next I tested out thinning the drops with alcohol and using canned air. I used the 90% alcohol on this whole project to see if I noticed any substantial difference to all of the projects I've worked on with the 70% alcohol. I covered the tile in small drops of a variety of colors. The ink doesn't spread much on these satin finish tiles.
So next I thinned the ink out with drops of alcohol from an eyedropper.
Then I used some canned air to spread the ink out. I kept dropping ink and alcohol and spraying the canned air until the tile was covered.
Then I used the eyedropper with almost no alcohol in it and sprayed it onto the tile to create this neat splattered/stippled effect. The ink seemed to react more sensitively to this tiny amount of alcohol when it was 90% alcohol than it did with 70%.
When I was done, I was left with two cool looking tiles that could easily be turned into coasters (just seal them with mod podge or clear sealer and put a little felt on the bottom). I also determined that, for the most part, 70% alcohol works just fine, but if you're doing a project where you want to really make the most of the effect the alcohol has on the ink, you might as well give the 90% alcohol a try (especially if you can find it for the same price).