What Type Of Resin Casting To Use On Top Of Plaster?

brama

Hi Everyone,
I have a problem and am so confused so I found this board and am hoping someone can advise me.

Here's me deal: I cut a tree down (about 5 feet tall), peeled the bark off, dried it, sanded it smooth as can be, stained and then polyurethaned it. I did that several years ago and am just getting around to doing something w/ it.
I intend to attach/hang some of my Tillandsia plants to it. So recently I got an 8.5" round plastic plant pot, placed a wire network around base of tree, put tree in pot and poured about 4.5" of plaster in. It set up very hard, I primed and painted the plaster white, the tree is anchored in and I'm very pleased.

Now what I want to do is pour some casting resin on top of the plaster to give it a thick (maybe 1/2") glass like coating to match the tree and prevent any potential water drips from seeping into the plaster.

I don't know if I should use polyester resin or epoxy??

The polyester sounds better since I can pour it all in one thick layer, but from what I understand the resin shrinks away from the sides of the "mold" after curing and I don't want it to do that.
I won't have a mold and the resin is intended to stay in the pot, so could I go in after the first layer cures and just pour some more down and around the sides of the pot where the resin shrank away from (and hopefully filling in any spaces there and around the tree base), or would that end up shrinking too?
I assume the second pouring just into the spaces would fill them, but I really have no clue.

Another problem with the polyester is that they say it very well may remain tacky unless I spray it w/ a resin sealing coat. Not a big deal but just another expense and step I'd like to avoid if possible.

The epoxy sounds good since apparently it dries very hard, non tacky and clear but you can only pour 1/8" thicknesses at a time if you go over 1/2 " they say it will turn amber colored, which I don't want.

I also don't know if these resins can be poured onto plaster. I don't want any strange chemical reactions or whatnot. Does anyone know if this would be a problem? I've read to seal any porous surfaces with a few coats of white glue, but it doesn't mention plaster.

I'm thinking of getting one of these:
The polyester:
http://www.pearlpaint.com/shop~ocID~~parentID~2972~categoryID~2970.htm

Or the epoxy:
http://www.pearlpaint.com/shop~ocID~~parentID~2972~categoryID~2968.htm

Can anyone advise me on which would be better for what I'm looking for? I'm sure I'm making this all too complicated but this resin is totally new to me and I don't want to make an unrepairable mistake.

Thanks very much for any help.

artyeva

your project sounds really interesting - i'd love to see a photo of the finished article!!!!

i haven't done any of this kind of stuff since art college, but one thing struck me, if you're worried about cracking due to shrinkage, why not start off with a thin layer of plaster sealant, something like this? This would give you the waterproof barrier that doesn't skrink, that you could then add your thicker layer on top of.

Just an idea!!! :rolleyes:

brama

Thanks for the reply artyeva
I can post a pic of what I have done so far if you want. I think I saw a picture posting forum here, or maybe I could just post it here... I'll look into it.

Thanks for the suggestion about the plaster sealant. I had read that I should seal it and (I forget where) they said you could use 4 parts white glue to one part water as a substitute sealant.
I'm in the US too so I'd probably have to find a sealant a little closer unless I wanna pay to have it shipped. I'm willing to pay, one day, to have a Mathmos lava lamp shipped over but not the sealant.

Anyway, I just ended up ordering the polyester resin. I hope it works out OK! I'll take a few pics in the day light of what it looks like now and see if I can post em.
Thanks again.

artyeva wrote: »

your project sounds really interesting - i'd love to see a photo of the finished article!!!!

i haven't done any of this kind of stuff since art college, but one thing struck me, if you're worried about cracking due to shrinkage, why not start off with a thin layer of plaster sealant, something like this? This would give you the waterproof barrier that doesn't skrink, that you could then add your thicker layer on top of.

Just an idea!!! :rolleyes:

artyeva

to be honest the white glue/water mix - although it will seal the plaster, may 'peel' - i have seen this happen over time. the glue 'breaks down' or something far more technical and chemical than i can explain!!!

if you're using something else over it, you'd definately need to check if they're gonna react to one another....!!!! :eek:

if the photos are on a web-album like flickr juct click on the ''insert image'' icon when you reply and then insert the URL of the image

brama

Yes, I see what you mean about the chemical thing happening. I was afraid of something like that w/ just the resin going on top of the plaster, but I can see it also melting, or worse, the glue. Unfortunately I already painted the plaster w/ regular primer and then white paint over that so I don't know if a plaster sealant would even work now..
I was planning on just painting the glue mixture over the paint as extra "protection" from the resin. Now I don't know if the resin will have a problem going straight onto the paint... I hate when it's not simple!

Well here's the pics I took. Just the tree in the pot, and the last pic is the close up of the tree embedded into the plaster. That's where I want to pour the resin.

artyeva wrote: »

to be honest the white glue/water mix - although it will seal the plaster, may 'peel' - i have seen this happen over time. the glue 'breaks down' or something far more technical and chemical than i can explain!!!

if you're using something else over it, you'd definately need to check if they're gonna react to one another....!!!! :eek:

if the photos are on a web-album like flickr juct click on the ''insert image'' icon when you reply and then insert the URL of the image

artyeva

it's a gorgeous looking thing - i love the lustre that the varnish has given the wood!:pac:

sorry if i seem to have confused you more!!

artieanna

The best thing you can do from what I see is to experiment a bit on a small scale using the plaster in a small container and then adding the resin etc on top. This will help to give you an idea of what the outcome will be. You could also try exterior varnish applied in a few thick coats, as it may give you the seal you want.

You don't want to risk spoiling it now it looks this good so take the time to see what will work for you!;)

I really like your Tillandsias :cool: are they difficult to grow?


Sorry I can't help more......

yank_in_eire

You could try gloss-coat surfboard resin. It cures hard (no tack thanks to a wax dissolved in the resin) and clear as water (if you don't stir too much air in when mixing it) and doesn't shrink much and is 100% waterproof. The downside is that the wax layer that floats to the top of the resin to allow it to cure hard will give you a slightly matt surface unless you polish it off and the resin stinks to high heaven until it cures fully!! You would have to keep your tree outside in a shed or at the very least covered in plastic on a balcony or porch until all the fumes dissipate. Another option would be clear gelcoat - but you would have to use surfacing tissue to get it to cure without being tacky and it can be difficult to get a smooth surface with that. You can get either from www.grs.ie
Hope that helps

brama

Thanks for the further replies everyone. I received the polyester resin in the mail yesterday so I'll just have to experiment w/ it on a sample first like Artieanna suggested.
If I don't ruin it I'll post a finished product pic.

Artieanna: Thanks, I love the Tillandsia's and have become addicted.
No, they're not really hard to care for. They just need bright light (which I don't have enough of indoors) and water (which indoors means taking them down and wetting/dunking them in a bucket about twice a week). No soil... very cool plants indeed. :cool:

They do much better outdoors apparently (and would be way easier to water by just spraying w/ the hose) but I like them inside and it's too cold right now for them to be out... so in they shall stay!