# resin background



## ben1988 (May 2, 2009)

I was thinking of trying to do a resin background for my 150gl tank.... I thought if i could layout a rock formation that i like using actual rocks and make a cast using plaster. I could then use some resin to coat the cast and have a resin background that has the actual texture of rock.... It would probably have to be two or three pieces...

I know many have done foam and cement but i am not one for creating artsy like things and have a non-exsistent flare for this sort of thing..

So what do you guys think? the only thing i am trying to figure out is how to keep the resin only 1/4 thick over the entire surface?


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## R-DUB (Jun 3, 2007)

My only concern would be; the final cast is hollow. This would create a "dead" spot behind the BG. Which would be good for hiding pumps,heaters etc.. but would also create a problem for cleaning and keeping fish out. Unless the final cast is filled with something. Or it fits very snuggly to the back wall of the BG. The look would be very nice though. Good Luck!


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## ben1988 (May 2, 2009)

i planned to cut a few holes and silicone some plastic mesh to the rear of the background thus creating a way for water flow to get behind the background to the filters and stop fish from getting behind it. The top would be open but above the water line so no fish could swim over it. I am hoping that i can make a few of these and maybe sell them for cheaper than some of the other resin backgrounds out there....


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## bell (Dec 12, 2005)

Instead of just resin you may want to use duraglass or gorilla hair (it's resin with "hair" in it basically) as it'll be more structural and won't crack easily, downside is you'll need more imo so the cost will go up....the closer you can get the final shapes with the first pour the less labor you'll have.

I would lay out the rocks first, coat it with mold release wax, then lay on glass/resin to make a mold. 
Then separate the rocks from the mold, coat the backside with release wax, then lay your matting/resin. The result will be an exact copy of how you had the rocks layed out when you. Off the mold....
It'll take a bit longer but the end result will be an exact copy of what you layed out...


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## ben1988 (May 2, 2009)

i think we are thinking the same steps bell just differant materials...I was thinking of using that rubber mold stuff and using that for a reusable mold instead of using resin. what do you think of that way?


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## bell (Dec 12, 2005)

Should work fine, but you're going to want to make it rigid or it'll change shape when you try to ma 
Ke a copy. After you pour it on and sets up I'd use either great stuff or duraglass on the backside to keep it's shape solid, make sure you get all the voids...
Did that make sense? LOL


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## ben1988 (May 2, 2009)

I am going to use the rubber to mold the rock, then use the expanding spray foam on the inside of that to make it rigid then paint the resin on to the exterior of the rubber to make the actual rigid background.... then seperate the foamed rubber from the resin....


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## bell (Dec 12, 2005)

Yep that'll work, make sure you use a release wax (coat the **** out of the rubber piece) of some sort or you'll rip the rubber when you separate it.
Also mix in some fiberglass matting when you lay the background piece, resin alone can crack as the mixture cools, I use shredded glass (like individual strands about 1" long) and it works very well with a thick resin coat, tha mat type will work but you'll need to cut into small pieces.


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## ben1988 (May 2, 2009)

how would it be best to create deep cracks and crevices that make places for fish to hide? or could i even do this?


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## bell (Dec 12, 2005)

place your rocks where it'll give you some crevices, when the rubber stuff is dry just make sure you get your expanda foam in the crevace to hold it's shape. 
for caves you can either make a second mold or just pick a section of the big mold to make a piece for a cave, then bond it where you want it using more resin when they're both cured.

using fiberglass gives you this flexibility as it'll easily bond to itself and not float


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## ben1988 (May 2, 2009)

will the fiberglass conform to the details of the rock? or are you talking about the hair stuff like before?

I guess the other problem to address would be that if i get too deep of crevices that i could not get the rock back out of the mold once its dry. So it would just be carefull placement and size i guess...


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## bell (Dec 12, 2005)

Here's what I would do.....
lay out a 2x4 frame the same size as the tank where the background will go.
Then fill the bottom up with sand and place you rocks on them pressed into the sand pretty good (you'll understand the sand in a second).
Then take any type of spray on car wax and spray the **** out of it, then take your mold release wax and coat the rocks the best you can (the spray wax will coat the top layer of sand).
Then mix a batch of duraglass (it's like resin with the hair in it) and spread it onto the rocks and in the crevaces (resin may be too thin and will encompass the rocks making you dig them out later) the duraglass will seep around them too but will be more workable.
After the duraglass starts to setup check for thin spots and add some more, you' want it thick so it'll survive the separation.
After it's cured you can used some spray foam to back it, but work it smooth.
Unsecure the 2x4sand carefully flip the mold over.
Remove rocks, some will fight just be carefull if you pry.
After all the rocks are removed you can wax it (use a generous coat of wax) and lay in resin and matting to create the background, I'd do at least 2 layers/coats, when it's all cured (an hour or so is enough for this step) you can separate it from the mold, you'll need to pry here or there and smack it around but it'll separate as long as you used enough wax.
Then you can cut out your openings for drains or whatever. And paint.

You could probably get away with 1 gallon of duraglass but I think 2 may be needed.......the rubber stuff you mentioned may work but I'd be concerned about it seeping down into the rocks......


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## iceblue (Apr 27, 2004)

Towards the bottom of this thread is a background Lomax made of fiberglass and resin. Unfortunately the original thread of the build no longer exists. If I remember correctly he used actual rocks to mold over and then added detail using different colored sands mixed with resin.

http://www.cichlid-forum.com/phpBB/view ... c&&start=0


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## ben1988 (May 2, 2009)

i went to the local body shop that does a lot of fiberglass repairs... They recommended that i just use bondo hair for both BG. They say that for the rock i brought it to show what i wanted to do the matting would not allow me to get much detail other than the deep cracks.... He also recommened i get some tire wax shine and coat the inside of the mold with that using a paint brush to really coat it.....I just dont know how i am going to get the tire shine off the mold and clean?


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## bell (Dec 12, 2005)

he basically said everything i said.....
duraglass, bondo hair, gorilla hair....all the same stuff basically.....
wax is wax....as long as it's a good coat.
you could actually get all the detail of the rocks, you would want to use a strait bondo/resin mix (75%bondo/25%resin) and use a plastic spreader to really get into all the nook and crannies, when that dries (cause it'll be thin) do the bondo glass coats, what you'll be left with is a durable mold with a perfectly mimic'd surface.....

here is a thread from another forum where i have pics from when i made the rear section for my cafe bike.......about halfway down with the red bucket, you'll see what i mean as far as application....using the bondo/resin mix will get you the details....

http://forums.pelicanparts.com/showthre ... afe&page=4

after you separate the bg from the mold you can hose it off and for the mold you'll want to hit is with a hose/toothbrush to remove any tiny rocks which may stick....


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## ben1988 (May 2, 2009)

I am going to try it on a small scale with just one rock and see how it all comes out tomorrow..

Could i make two molds and then sandwich them together with a 1/2 inch gap all the way around by drilling holes and then using bolts, washers (to create the void), and wing nuts, to create a "void mold" where i could just pour the bondo-hair into the void and then let it sit to cure or does bondo hair stick fairly well?


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## ben1988 (May 2, 2009)

OK so i got the wrong stuff yesterday...I bought plaster repair not plaster paris. The store was already closed so i gave it a try.....DO NOT USE PLASTER REPAIR COMPOUND!!! it creates large cracks when poured in large amounts. I am going to buy some plaster of paris today and try to make the molds again.

I am still unsure if bondo hair will cure when in a sandwich mold.....also i am going to add sand to the bondo-hair to try and make it look more brown and rocky looking. I am going to try and get some gray, red, brown and white sand to blur the colors a little and also i have heard that adding sand one makes the resin go farther with less, and it helps to disapate the heat generated by the chemical reaction (also i think that it being in a sandwich mold the heat will be worse and create large fractures).


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## bell (Dec 12, 2005)

The resin will fully cure no matter what as it's a chemical reaction and does not need oxygen to cure.
you won't get any cracks, it is important to not get any bubbles though so work it in thoroughly.......


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## ben1988 (May 2, 2009)

Well i got a 25lb bag of plaster paris today (free  ) and i also went to local landscape place and worked out a deal to "rent" about 30 rocks to lay out for the background. cost me 25 bucks up front and when i bring em back i get 12.50 back. i decided that i am going to try and sandwich the resin with two molds... small scale testing continues tomorrow :?


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## ben1988 (May 2, 2009)

ok guys i got a good start on the plaster mold process today. I built a wood box with no bottom and then placed about an inch to and inch and a half in the bottom. Then i started laying rock into the box to get the look i wanted. I forgot to get pictures of the box process but here is the center focus rock already in the box....









with a few more rocks in...









and then i proceeded to finish it all up and here is what i have made my mind up with and changed several times lol.....
top (what will be front view)









left side









middle









right side









the largest rock is about 5 to 5.5 inches (after being sunk in the sand) deep.


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## ben1988 (May 2, 2009)

and we have monetary failure :x the cost is going to be too great..... was given one 25lb bag of plaster thinking that would be enough i mixed and poured it onto the mold.....not a chance drove like nuts to the store bought three more 25lb bags to try and salvage the mess...still not enough plaster to cover the rock still had near two inches left to fill in on top. next idea.....

think spray foam will release the stone with wax added?


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## bell (Dec 12, 2005)

you know i've been thinking of different ways to come up with a mold......and think i have something.....

paper mache, i've done a lot of this in my past (think grade school LOL) and i believe you could make a heavy paper mache coat (lots of wax on the rocks) then back it in bondo hair, remove from the rocks, then coat the front with resin and that would work, the biggest thing is to have a rigid mold which can be waxed, and nothing is cheaper than old newspaper and flour.......

i would also move your rocks closer together or dig some trenches where the sand is flat, too flat can make it look not real....

i'm going to think more about this, but have been inspired as i need to make the background for my 180........


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## ben1988 (May 2, 2009)

hmmmmmmm....


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