Hey, for a mere 3 Large it’s yours! 
According to this, the ideal is Lexan:
The person in that article is doing the same thing as you, more-or-less; in your case you are using 1" graph paper, in the article it’s a music teacher with a musical staff underneath the writing surface to write music notes on. Note that the article warns not to use acrylic (which would be cheaper) because it tends to leave “ghosts” behind after you erase the marker.
The problem is that from what I can tell, Lexan is pretty expensive. They don’t come in 5x9 or 3x5, but you can get a 4x8 (so you’d have 6" of uncovered space on every side) for about $175 at Home Depot.
I found it much cheaper on Amazon, it’s not the Lexan brand but it claims to be the same material. It’s $100.
https://www.amazon.com/Polycarbonate-EasyRuler-Resistant-Plexiglass-Industrial/dp/B08SWRXH7K/
Again, not the perfect size for your table but close.
As an alternative, why don’t you use a gaming mat like most gamers? My group has used them for decades. They come with the grid on them (and are sometimes reversible with squares on one side and hexes on the other), are designed for dry erase or wet erase (depending on the mat). I’m sure it won’t be as durable as using polycarbonate over grid paper, but it is easier to work with. Here is one that is really big and should cover most of your table:
https://www.amazon.com/Chessex-Mondomat-Double-Sided-Reversible-Playing/dp/B00125FBN8/
It’s 4.5’x8.5’. Almost the perfect size for your table. It uses wet erase markers, not dry erase, but it works well. We’ve had one of these mats (same brand, Chessex) for more than 20 years. Just clean off the marker with clean water from a spray bottle and a rag and it won’t leave ghosts behind.
I’ll look into Lexan options. Thank you.
I swear they didn’t used to make mats that big even 6 years ago or I might have gone that option.
I’m not sure if this is true, but a buddy at work says that dry erase markers are just regular markers with acetone in the ink. We started using regular sharpies, and erasing with acetone. It works.
Lady at work taught me a big time game changer: Mr. Clean Magic Erasers.
I just use sharpies and magic erasers on whiteboard now.
Aren’t magic erasers just a very fine abrasive? If so, are you just scratching up your whiteboard by using them to clean it?
Magic erasers sure are abrasive.
I’ve been using them on whiteboards and laminated worksheets for a couple years now with no sign of damage…yet
Yeah, I don’t think that’s true.
I once cleaned a white board with acetone and I was never able to erase dry markers from that board again.
I think the acetone took off some sort of coating that allows dry markers to be erased.
Smartboards (of whatever brand; I’ll admit that I’m not familiar with Clevertouch) have their own issues. The resolution is often poor, the kinds that use a projector can easily get out of alignment, with most of them you can’t have two people writing at once, you can’t use your finger to erase a single tiny mark, it takes time to start one up, and like any technology, they’re more failure-prone that a whiteboard. The newest generation use a large screen instead of a projector, and are basically very large Android tablets, and solve many of the problems, but the drawback there is that they’re not as big as the projector-based ones.
All that said, of course, they also have their advantages, and they’re getting better all the time.
Nope. They aren’t.
As to why they are erasable only from certain things…
Dry erase markers are only compatible with non-porous surfaces. When using this type of surface, print only resides upon the outermost layer of the board. This allows for the marker to be easily erased, without damaging the integrity of the dry erase template. If you’ve ever gotten dry erase ink on your clothes, you know that dry erase markers can stain. If a dry erase marker is used outside of its conventional use on a whiteboard or a similar writing surface, the ink soaks into the surface, functioning just like a permanent marker.
So no, it’s not a regular marker with acetone added. As to what a regular permanent marker is made with:
Permanent markers are made up of three components: colored pigments, a solvent (be it water, alcohol, or another solution entirely varies on a manufacturer to manufacturer basis), and a polymer. Permanent markers commonly use an acrylic polymer in their ink, which helps the marker stick to the writing surface. The polymer, in addition to the solvent and pigments, is then mixed to form the ink of the marker. The ink is then stored in a polyester reservoir that helps contain the ink inside the plastic casing of the marker.
So the difference is that dry erase markers have a different polymer than a permanent marker. That changes what the ink will adhere to/soak into.
I suspect the acetone changed the surface so that it was no longer non-porous (removing the top layer as you suspect), and the dry erase markers were then able to properly soak in and stain it.
Thanks for the info. I’m gonna show that to “dry erase markers are regular markers with acetone” guy at work.
I don’t think the acetone did any damage to our whiteboards, but it would leave a white grainy finish on laminated papers and tags. That’s one of the reasons we switched to magic erasers.
As a taxpayer, you’ll be proud to know that we have spared no expense in getting high quality devices. LOL
A bit of a digression, but what is that which leaves the lettering raised, often seen in graffiti:
It looks like acrylic paint used in a pin-tip marker, but the paint in pre-filled acrylic markers usually seems much more fluid.
I’ll offer two guesses:
There’s a style of painting where paint is squeezed directly from the tube onto the canvas.
There are some products made to decorate fabrics - “dimensional fabric paints” - that produce this raised effect.
It just looks like it was written with a puffy pen.
If you had a heat source handy, you could have checked to see if it “puffed up like popcorn”.