Cracks in water based wipe on poly after curing for a few days

[Changed5Times]

Any idea why these random cracks are happening?! This is with Minwax water based wipe on poly (the gloss one). They only appear a few days after applying the poly.

I've tried flat sanding over them (a huge pain since they run fairly deep) before applying more poly, and I've tried just applying poly over them, which seems to smooth them out, but the problem is that in either case, I always wind up with more of these lines (a few newer ones show up each time) after applying more poly! So I thought to seek advice here before proceeding.

Applying too much at once? Not waiting long enough between applications (I wipe on a few coats, wait a few hours, repeat a few times, set aside for a few days)? Poly is too old (bottle has been open for > 1 year)? Poly is not well mixed? Something else?

 

[Bruce Johnson]

Any idea why these random cracks are happening?! This is with Minwax water based wipe on poly (the gloss one). They only appear a few days after applying the poly.

I've tried flat sanding over them (a huge pain since they run fairly deep) before applying more poly, and I've tried just applying poly over them, which seems to smooth them out, but the problem is that in either case, I always wind up with more of these lines (a few newer ones show up each time) after applying more poly! So I thought to seek advice here before proceeding.

Applying too much at once? Not waiting long enough between applications (I wipe on a few coats, wait a few hours, repeat a few times, set aside for a few days)? Poly is too old (bottle has been open for > 1 year)? Poly is not well mixed? Something else?

View attachment 4847157

Hmmm......I really don't know. Is this the Minwax Polycrylic or Minwax Water-Base Polyurethane?

My guess is that the cracks are from slow curing; you are putting on coats too quickly before the coats underneath are fully cured.

 

[Beej]

I'd guess the same as Bruce. I've used a lot of waterbased finishes and to be perfectly honest, the Minwax Wipe-On Polycrylic was not great. My main issue with it is hardness, but I've had drying issues with other water based finishes I've used as well.

What's your entire finishing process? From final sanding grit to dry time before recoating? I know that Minwax states good to recoat in 2-3 hours, but in my location which is quite humid, most waterbased finishes needs to dry for around 5-7 hours before I'm able to recoat.

Sorry you have to deal with this, finishing can be a struggle!

 

[Changed5Times]

Thanks @Bruce Johnson and @Beej.
This is the water based wipe on polyurethane. Based on what you're saying, I'm probably too aggressive on building it up and/or with the recoat times. The problem (and this why I can't state here my exact process) might be due to that I'm very familiar with shellac, and in my experience you can pretty much do whatever you want with it in terms of build/recoating. Combined with that this is the first build that I'm actually trying to complete on a schedule (my daughter painted it, and I'd like to have it ready for her birthday), so I'm probably rushing things as well.

This didn't occur when I tested the Minwax on scrap - I actually really like the performance of this product from what I've seen - but that was on a small scrap of wood. For now I might just switch to a product that I'm more familiar with.