# anyone else use polyester resin to seal wood? here's what I did



## jessesnowden (Mar 15, 2015)

Hello all!

Just registered here so I figured I'd share something before I start asking for free info

I'll give a quick rundown of my current project:
Wood panel shower insert (pallet wood)
Tile tub
Exposed copper pipe w/ waterfall shower head

Right now I'm on the wood. In my quest to find the best way to truly waterproof wood, there have been a lot of dead ends. Since the wood will be in direct contact with standing water for years on end, whatever I do will have to be virtually sea-worthy. After reading a handful of write-ups and stopping by my local boat repair yard I have something really cool to share with you guys!
Polyester resin, diluted about 5:1 in acetone. With about 10x as much hardener as directed (since it's so diluted you need a lot to get the full reaction)

I wanted to try it out before dropping big bucks on marine grade sealants from the boat yard. I Picked the guys brain at the boat yard and he said he and a few other shops use this same mixture to coat new wooden pieces. inside and outside. They would usually put on a final coat of something heavy to give it that glossy look, but this is his all-purpose tool for sealing bare wood. 

I tested it out on a little bench I built the other day for my fire pit. After only 2 coats water beads off all day long. The particular write-up I found suggested to just keep on putting down coats until it doesn't take any more. Which I will do for the shower. The wood still looks totally natural but wet. Only slightly glossy. Still able to sand, basically the wood has become fiberglass.

Hope this helps someone somewhere someday.

Cheers!

Pics of the bench and shower wood in progress


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## Steve Neul (Sep 2, 2011)

The fiberglass resin is alright to finish with but doesn't brush on very good and doesn't look nice like a varnish but it will waterproof. You shouldn't use an excess of hardener. This will make the resin more brittle and more likely to crack with normal wood movement. I wouldn't dilute it either, just use as directed. Fiberglass may look glossy when it is fresh however won't stay glossy. It's really not formulated for a finish, it's formulated to use with fiberglass cloth or mesh to make a solid material. If you are looking for a nice glossy waterproof finish use Epifanes varnish.


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## epicfail48 (Mar 27, 2014)

Nice trick mate. For better results though, you may way to look into an epoxy resin instead of polyester. Behaves the same, but its stronger. Little bit more expensive, but hey, fiberglass resin aint cheap either!


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## InnovativeSnC (Mar 12, 2015)

I completely agree with both of the responses you have received, they have great advice.

Steve Neul had it hammer on the nail with not wanting to dilute your resin. It will weaken the chemical properties of the resin. Also for most polyester resins, I believe the ratio of hardener is around 1% ( meaning it will take a long while to cure, but will eventually cure ) to around 2.5% ( meaning the pot life of the resin will be shortened drastically so do not waste time applying, and the part will respectfully cure faster. ) Maybe try using a small roller, and don't be scared to load it up with resin, the wood will absorb some anyways. You could always sand the resin down after it fully cures, to about 320 grit and then clear coat it with products like Awlgrip. ( but it will not be the cheapest route )
Also, I would agree with epicfail48. Epoxy would be the best way to go, but it is more expensive. However, they do make Vinyl ester resin, which is greater than polyester in terms of 'waterproofing' and strength. These are just some helpful tips for you to remember next time you use resins, because as epicfail48 mentioned, they are costly!

If you ever need some advice in the future feel free to message me, I would be glad to help the best I can. 

-Innovative Saunas & Cellars Inc.


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## RandyReed (Jul 30, 2014)

jessesnowden said:


> Polyester resin, diluted about 5:1 in acetone. With about 10x as much hardener as directed (since it's so diluted you need a lot to get the full reaction)


Is that 5 parts resin to 1 part acetone or do you mean 1 part resin to 5 parts acetone (1:5)???

Like other suggestions, epoxy resin would be better.


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## jessesnowden (Mar 15, 2015)

Thanks for the input guys, I will try to refine my recipe a bit to see if it can be improved. But i gotta tell you guys, this mixture of 5 parts acetone to one part resin and a big squirt of hardener has been giving me exactly the results I've been looking for. 

I tried this for the simple fact that it WAS cheaper than epoxy or any of the high grade marine products. This was an affordable work around for water proofing. Ya'll should try it and see how you like it!

I'm using the cheapest stuff i could find. $20 for a quart of BONDO resin and $16 for a gallon of acetone at Lowe's. 

Cheers!


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## Steve Neul (Sep 2, 2011)

When you refine your recipe keep in mind the chemist at the factory that made the product has already formulated the recipe to the best it can be. A lot of finishing products you can modify to make fabrication easier but in the process ruin the durability of that product. You would be better off to use it as directed.


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## RandyReed (Jul 30, 2014)

jessesnowden said:


> Thanks for the input guys, I will try to refine my recipe a bit to see if it can be improved. But i gotta tell you guys, this mixture of 5 parts acetone to one part resin and a big squirt of hardener has been giving me exactly the results I've been looking for.
> 
> I tried this for the simple fact that it WAS cheaper than epoxy or any of the high grade marine products. This was an affordable work around for water proofing. Ya'll should try it and see how you like it!
> 
> ...


Ok that sounds more like it. 1:5 with acetone is about right.


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