Having that grayish patina can look awesome and add a distinctive look to your piece. It adds age. You can purchase all kinds of expensive products that will do the same thing, but this has got to be the easiest way yet. As long as you can afford at least 4 days to let the solution work, you can create this aged wood look in less than an hour.
First Step - Find a clean pail with a tight fitting lid. Enough to hold your vinegar and equal amounts of water.
Second Step - Wearing protective gloves, tear apart the steel wool and place in the bucket.
Third Step - Pour your plain white vinegar into the bucket (this works on a 50/50 solution of vinegar to water so make sure your bucket is big enough and it also depends on the size of your project as to how much you need) Do not use the water just yet.
Fourth Step - Let these two ingredients soak (steel wool and vinegar) for at least 4 days.
Fifth Step - After 4 days check it out, it will look all muddy and rusty. Add equal amounts of water to the solution as vinegar and stir with a paint stick. (In the video she used a 1/2 gallon vinegar and used the same bottle for the water)
Sixth Step - Using a clean paint brush, paint the solution on your unfinished wood and watch the magic start within an hour.
That is it! Check out this video for a more visual look.
It can take years to have wood turn that silver/grey look. I used to look for old barn wood, and now many antique stores sell it, but it gets very expensive. If you don't mind a bit of work, for the price of some white vinegar, steel wool, a bucket and a paint brush (you may even have all of these items at home!) you can knock that "too new" look right off the unfinished frame.
Unfinished Wood Works Best for Aging Wood
You could try and sand an old piece of wood or frame to get every bit off, and give it a try, but so far I have found better luck with new pieces. You can get plain wood frames online, or you can make them yourself. Get the cheapest pine and then get creative with this aging process. As you can see in the video, it can really give that rustic look you are going for.
If you sell your artwork at shows, fairs or even give as gifts, framing can get very expensive especially if your work is a unique size. To keep your costs down, try to keep your artwork to such a size that a common sized frame will work. Especially if you sell it without frames (as I tend to do!).
An Entire Page of Unfinished Picture/Art Frames online
Customers don't want to have to pay a lot extra for a special made to order frame which can get very expensive. But if you do sell it framed, try this process instead of numerous coats of paint or stain.
Rustic Look to Frame Your Artwork
If you love the idea of a rustic looking barn wood frame but without the splinters, then get unfinished ones online as above, or find deals, just make sure they are unfinished so the vinegar and steel wool process will work its magic.
I absolutely love this patina, and it will pretty much match most decors as it is not too bright or too dark, just right.