Hurray you made a watercolor painting! Looks great. Now you want to digitize it. You scan it with your trusty scanner. IT LOOKS LIKE CRAP. You swear a lot and curse your scanner 😞.
Scanners have a weird way of collecting the data for watercolor paintings, especially for paintings done on cold-press or rough paper (what is normally considered 'watercolor' paper, with a texture, as opposed to smooth or hot-press papers).
Here's how I do it to preserve as much of the original painting as possible, and make it look nice for display or print reproduction.
Step 1 - Prepare the painting
Make sure your painting is DRY first. Like, really, totally dry. Leave it overnight to dry if you can. While your at it, FLATTEN the painting as much as you can. If you used a lot of water and didn't pre-stretch your paper, it will buckle (i.e feel all bumpy) when it's dry. Flattening a painting is a whole other thing but you can read this article on how to do it.
Step 2 - Choose a scan direction
If you look closely at your coldpress paper, you'll see little depressions or bumps. These little bumpy bumps on the paper cast tiny shadows.
This is IMPORTANT because with coldpress paper, the scan can look different depending on the direction it was scanned in.
You can put your painting on the scanner horizontally or vertically -
The pic on the left was scanned with the painting on the scanner horizontally. The right was scanned with the painting on the scanner vertically. The texture appears different on both the white area as well as the color. Neither is really right or wrong, but you should pick which one you prefer and scan all the art in that same direction
Step 3 - Scan the thing
NOTE: It's impossible to say what scanner settings to use exactly because scanners are all different and the softwares have different settings. I use VueScan, because it just works and has better controls than the default software that came with my Epson scanner.
VueScan has a COLOR tab that lets you figure out the starting color balance. Usually, you want to pick the one that either gives you the closest color to the original painting, or the one that gives you the whitest white. I chose Neutral for this one. Other scanner software may have similar settings, especially if they come with some kind of 'pro' or 'advanced options' mode.
Make sure that you scan the image at a resolution that is high enough for what you want to use it for. If you want to make a print, make sure it's at least 300dpi. If you want to enlarge it, scan it at an even bigger dpi. Save the files in TIF or JPG (if you're not terribly concerned about compression).
If you have a really small painting (or you're rich and have a really large scanner) it won't matter, but chances are you will have to scan your painting in parts and stitch it back together in some software. When that's the case, you want to place your art on the scanner and then scan it to nearly but not up to the edge. Repeat as many times as necessary in order to scan the whole painting.
Don't scan it right to the edge. Scan to around the right edge of the red rectangle in the pic.
If you scan it right to the edge there will be a shadow and it makes it harder to stitch together the artwork later.
Step 4 - Join the pieces in software
If you scanned in multiple pieces, join them up (if you didn't need to, feel free to skip to Step 5)
I use Photoshop to do my edits but there are other image editing softwares with pretty much the same controls. However, my version of PS (2021) does have a (NOT AI) function called Photomerge which really speeds up joining scans together. This is a terrible video but its the easiest way to show how it works.
If you do not have PS or a similar software to automate this, you can merge things together manually as well. There's different ways to do this, which I'm not going to cover here. You can Google for some tutorials for your particular software. This one has an alternative method for Photoshop. This video is about joining artwork in Affinity Photo (I didn't watch it, I don't use Affinity)
When you are done joining the artwork, it should look something like this.
Step 5 - Color adjustments
It's looking pretty good (hopefully)! What you want to probably do now is color correct it so that it looks more like your original painted art. You may also want to get rid of the bumpy texture, at least on some parts of your image (or keep it, it's up to you).
What I like to do first is make a new layer and make a big white square on it. This gives a reference point on how white your whites are.
As you can see, the white square is much whiter than the paper, and certainly the blank area around it.
I like using Image > Adjustments > Selective Color. Under the Colors, choose White and reduce the amount of Black. Now the white areas look closer to the white square.
Then I like to use Image> Adjustments >Levels to adjust things further. I use it to make the white appear brighter, so now the white square and the other white areas are almost the same. I also use it to bump up the color areas, so they are now more saturated, like the original.
I find it's easy to go overboard with Levels, and for lighter colors to get eliminated this way, so try to move the sliders slowly to get the result you want.
And then, you should be about good to go! You can do further touchups for small areas manually, but at least the art should be looking more cleaned up and vibrant now. The left image is before color correcting, and the right one is after applying Selective Color and Levels.
Ok I hope that made sense and was helpful! If it wasn't then just pretend I didn't say anything and spend 2-3h making this lol sob
I DON'T WANT TO BUY VUESCAN TO SCAN
That's fine, you can use whatever scanner software works for you. The settings will be different but AFAIK Epson's default scanner software had pretty good options under the advanced settings too.
I DON'T USE PHOTOSHOP/ I HATE ADOBE
You can use another software to do your edits. I use PS so I only can write the instructs for that.
I TRIED TO FOLLOW BUT MY FINAL RESULT STILL SUCKS
There's a whole bunch of scenarios that might might affect things. For example if you have a lot of white areas but WANT to include the texture, but the paper is very buckled to begin with. That sort of painting might require you play around with the scanning settings to try to get the best result to start with. It may also require additional, manual touchups to even out the bump areas.