This is all good advice, … But what to do with the huge stack of proofgrade I already have? Is there any hope for good sanding results?
except the PG hardwoods are pretty limited. walnut, cherry, oak, basswood, poplar, maple. if you want something other than that (and the list is pretty long for options), it’s not going to be PG.
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Use it for projects that lend themselves better to 
. Proofgrade has its merits. Last night I spent 15 minutes using a utility knife to free stuff from 3/16" birch plywood. The laser cut through over 99% of the length of the cut lines. That still left tiny little spots where I had to finish the process with a utility knife. I spent most of last weekend sanding, staining and applying polyacrylic to sheets of plywood in hotter than balls weather. Monday night I masked them. Proofgrade really isn’t an option for what I’m making, but in my moments of weakness I thought, they need to offer proofgrade in colors (and yes I know about the wood gallery’s colored plywood - still not what I need.) because I really don’t care about my money.
I’m sure you’ll eventually find projects where proofgrade is the best option.
I did sand off the finish on some proofgrade hardwood soon after I received my glowforge. I was doing inlays and needed to sand everything flush, plus the inlay parts weren’t finished. I used 120 grit to remove the finish and then 220 prior to refinishing. I did not use any stain. Have you tried your unicorn spit on a regular old piece of sanded wood and then apply masking and peel it off? Stain pretty much just sits on top of the wood. It should not pull up with a masking tape, but that is the first thing I would try in troubleshooting this problem.
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PG has a very thin veneer layer. I would attempt to chemically strip the wood before I would sand it. The PG is finished without stain, so you should get the natural wood color once the finish is removed. If you aren’t getting the finish completely removed, your additional finish layers will not be able to penetrate the wood fibers and will not adhere.
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mmm, Stripper… I hadn’t considered stripper.
"Have you tried your unicorn spit on a regular old piece of sanded wood and then apply masking and peel it off? "
Another good suggestion for troubleshooting.
That’s why I love this place. The Hive Mind.
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ZOMG, now I have to try that stuff! Curious how (if?) it will work with leather…
As to your original question, I’m going to echo the advice that others have given: I think you’ll see better results and use less effort to begin with an unfinished wood. Save the PG for other projects where it can shine, and where using pre-finished wood will actually save you time.
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That stuff is … every bit as magical as it seems… as for how it works with leather… I’m about to test that today. I’ll upload a pic.
People put it on fabric, wood, you can use a chalk primer and put it on anything. It stains wood and fabric but washes off your fingers like a breeze. It’s safe for kids to use. It’s super vibrant.
There is a bit of a learning curve (It’s water based, you have to use an oil or poly sealer). It can reactivate with water until it’s sealed. It’s super forgiving… but depending on the look you want, I recommend finding a tutorial to start.
The story is amazing too… Michelle, the inventor… she developed it in her work with disabled/senior adults… giving them something better to do than simple arts and crafts. Her brother ran an adult day care center. They loved it. Couldn’t get enough of it.
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Oh, please do! I just researched it a bit, and (as you mentioned) the stuff is not cheap. Would be nice to get a little preview before I invest 
That makes me love it even more! I’m a firm believer in the notion that art heals.
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Do you have a special place that you get your 12x20 birch for $1.00 or is is something that you can share the location.
Not super special.
Rugby building products. $14 and change for a 60x60” sheet, which cuts perfectly into 15 12x20’s. Sadly rugby doesn’t cut it down, unlike my previous supplier. Hopefully I can find another supplier because cutting the sheet goods down is a major hassle.
More info here:
The general idea is to find a local supplier and see if they’ll cut it down for you.
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Thank you for your help
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FYI, As some have commented. The PG finish is really durable and not easy to sand and when you do its very easy to blow right though the veneer and not notice it until you apply stain and get blotches. But if you must I recommend you use a wood scraper to get rid of most of the finish before sanding. But this will get expensive trying to get the results you desire. Also be aware that any chemical stripper you apply could also affect the glue bond of the veneer and the mdf core with undesired results.
For a more practical result search for other ply that is unfinished and you can achieve the results you desire. Yes it adds steps and in the end your cost might be similar or more than PF but it will be a much more stress free situation. If you live near a Menards I really love their maple ply for situations like this. Just be aware that you need to sand the ply on both sides prior to applying masking otherwise it peels easily during lasering. But you can apply stain and finish prior to masking and or afterwards as well.
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… but not too much. There’s a sweet spot on sanding for masking where it sticks just right. Sand it too smooth and that masking will be adhered to that surface and will likely pull up stray fibers from the wood when you try to remove it, necessitating more sanding later anyway.
I just barely hit my materials with 400 grit and get good results, ymmv.
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OMG, I just followed that link. These people are my people.
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@evansd2 is right and I forgot to mention it. I usually sand the panels right before I need them masked with the highest grit I have on hand usually 120 but a really used and well worn down disc on my orbital sander. Usually 4 passes, 1 short ways against the grain and 1 long ways with the grain and repeat. I only bother with higher grits if I am staining or clear coating otherwise most of my stuff gets paint and 120 is good enough. Hope this all helps.
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@Drea Well, here we are: Spit and sealed with NeverWet.
Typically, when you seal Unicorn Spit, you use something like Tung Oil or Polycrylic. It brings the vibrancy of the colors back. This came out still slightly chalky. However, the NeverWet does work as advertised… I couldn’t get that piece of leather wet if I wanted to. It just beads up and falls off.
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Very cool! Thank you for following up and sharing your experiment 
And, now I’m curious about this NeverWet stuff. Will have to check that out as well … not something I’d typically use, but I can think of a couple niche applications where it might be perfect. So thanks again - you’ve taught me two new things in one day.
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I find it easy to sand. not sure what y’all are doing wrong
Things may have changed in 4 years.
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