Inkjet printing papers have a special coating on the printing side that is designed to control the ink from spreading when it hits the paper and thus creating a blurred image. There are a number of ways to determine which is the correct side.
Method 1 – Trial and Error
Print a sample – if it is rubbish, you have printed the wrong side, flip over and try again.
This is wasteful and time consuming so only use as a last resort. To be more scientific, use method 2.
Method 2 – The Visual Test
The coating on inkjet printing paper is often slightly different in colour than the base paper itself. The aim is to make the printing side as white as possible and if you compare both sides, one normally will be brighter and whiter than the other.
On matt coated paper, the printing side is likely to be smoother and slightly chalkier than the uncoated side. It will also be a little whiter.
The most difficult to tell are the textured art papers which are very white on both sides. There is a subtly difference on the coated side which is going to be a little smoother than the uncoated side. You can sometimes also tell by running a fingernail across the surface. The coated side will catch a little whereas the uncoated side will appear to be a little smoother.
It almost goes without saying, double sided photo papers can be printed both sides.
Method 3 – The felt tip
Putting a small mark using a felt tip pen will also indicate which is the coated side. If you mark the uncoated side, the mark will spread or smudge, if you hit the coated side, it will stay solid and sharp. This is also a method which will destroy the sheets and should be used as a last resort but is quite effective.