Jim
Why do I always get scorched overburn marks on my basswood engraves? As you can see, it’s only on the “south” side. I’ve played with power reduction, speed reduction, some masking options. Is this an airflow or fan problem? Is that a magic silver bullet or toggle that I’m missing that will correct this. Most of the time, I just try and clean it off after the fact, but there has to be a better way to address this. Help..
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That is the re-deposition of the vaporized basswood (“smoke”), blown in that direction by the air assist fan.
Masking can protect from that for many applications. It’s harder with detailed engraves, where the masking may get totally destroyed.
People have various techniques for removing that, including wiping it off with isopropyl (rubbing) alcohol or hand sanitizer (which may soak in to the wood less), and sanding. Others will fill in with any I have missed.
Edit: More radical solutions include upgrading the air assist:
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Yes & no. It’s a deliberate design decision from way back. They wanted to have good marketing shots of the GF so they oriented the head’s air assist outlet toward the front. Unfortunately that is opposite the airflow of the main fan so it doesn’t get quickly sucked up and off your project piece. The forward blowing air deposits the smoke right on top of your engrave. Nothing you can do but mask or clean it off after the fact.
It was raised as an issue early on but marketing videos win over elegant (or even effective) design every time. 
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You’ll also find if you do a lot of acrylic engraving, the vaporized material will redeposit towards the front, and leave a rough surface.
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This is why Proofgrade basswood, and all other wood Glowforge offers, comes with masking tape completely covering both sides. You’re intended to engrave and cut with the masking on, which protects all the untouched surfaces from this charring/staining, then peel off the masking after taking the parts out of the laser.
If you want to use unfinished wood from other sources, you can add masking yourself before cutting or engraving it. “Medium tack paper transfer tape” is the name of the masking used for this purpose; it must be the paper type, not transfer tape made of plastic which is also available. Ex:
https://www.amazon.com/dp/B08563Q5ND
Or, as @evermorian covered well, you can clean it up after the fact with alcohol or some sanding.
If you use wood with a clear coat finish, this still gets that overburn, but it cleans off much easier than on unfinished wood. You can use some alcohol or a baby wipe and it’ll come right off the finish.
My personal preference is to apply masking to unfinished wood where I need to save money on the material, and no masking on finished wood that I quickly clean with alcohol wipes for higher value products.
I use alcohol prep pads as cheap disposable alcohol wipes for cleaning work:
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Excellent advice from @dan84 about masking. For some more detail on the topic, #2 on my faq gets into some alternate sources and usage tips.
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Awesome! Thanks for the advice. I do have some of the transfer paper but haven’t been using it consistently. I’ll try it.
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