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Thread: 3D background help

  1. #1
    DIYFK member Simon1991's Avatar


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    3D background help

    Hi all

    As the title states I need some help to make a 3D background. I'm going to go down the polystyrene carving route as this looks like the easiest way rather than fibre glass mould.
    Plan so far, get a shed load of polystyrene, use a fish safe sealant to stick the sheets together to get desired thickness, cut and carve the polystyrene to the desired shape. Sand down polystyrene and then cover with cement, wait for it to dry and add paint.

    If this is correct I have a few questions regarding this:

    1. Do I use cement?
    I've watched a few tutorials and some have and some haven't used cement to cover the polystyrene. I know cement will raise the pH of the tank for a while having to do regular WC's to bring it back to normal. Is there a better option and is the cement required, if so what type?

    2. Sealing after paint
    I will be using 100% Acrylic paint to try and make the background look as natural as possible. After painting should I be sealing it with anything or will it be okay?

    Any better methods, if so let me know

    Thanks


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  2. #2
    DIYFK member Meep's Avatar


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    Cement isn't required but it will add weight and rigidity to the build, other options include epoxy resin or some even use basement sealer paint (Drylok) to cover the foam... Once hardened (as in fully cured and stabilized by long-term soaking) and sealed with paint the cement will not affect the PH much if at all...

    I would seal the paint job with Krylon Fusion clear coat to help prevent pealing...

    As for better methods, there are certainly alternative methods, but skill set, cost and whatever all come into play... Cement coated foam is probably the easiest... If I was doing it since I have a background in molding and casting, I would probably fabricate the entire background using whatever fit the bill for the look, then pull a mold off it, then cast a resin or fiberglass shell out of the mold, but that is a lot more money, skill and time investment...

    Another thing to consider with the cement and foam build is to laminate the cement over the foam, basically you cover the foam with plastic wrap, then take burlap or another similar cloth that will soak up the (soupy mix of) cement, cut that fabric into small pieces and strips, then dip in the cement and layer it on top of the plastic coated foam, similar to paper mache or fiberglass layup... Do 2-3 layers of this then flip it over and chunk out the foam, leaving you with a thin fiber re-enforced cement shell... This is the technique most used by zoos, theme parks and what not to build faux rock structures...

  3. #3
    DIYFK member Simon1991's Avatar


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    Thanks is there a way to make a background that wonít change your pH?


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  4. #4
    DIYFK member Meep's Avatar


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    Click here to enlarge Originally Posted by Simon1991 Click here to enlarge
    Thanks is there a way to make a background that won’t change your pH?
    Sure make it out of fiberglass, resin, foam with something besides a cement coating, vacuum formed plastic over a buck to name a few...

  5. #5
    DIYFK member Simon1991's Avatar


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    Okay thanks. So if I make it out of fibreglass can I reuse the polystyrene to make another or will it get damaged when taking the fibreglass off?


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    DIYFK member Meep's Avatar


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    Typical polyester fiberglass resin will instantly melt the foam... If you want to fiberglass over foam you need to first seal the foam, and it's essentially a one try process... If you want something to pull multiple copies you need to pull a mold off of the foam, then lay the fiberglass into that mold, a lot more involved...

  7. #7
    DIYFK member Simon1991's Avatar


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    Thanks mate! Okay so what could I use to make the first initial mould?


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  8. #8
    DIYFK member Meep's Avatar


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    Click here to enlarge Originally Posted by Simon1991 Click here to enlarge
    Thanks mate! Okay so what could I use to make the first initial mould?
    If I was doing it, I would probably create a silicone mold but it can be costly to create one, but there are other options as well, like urethane rubber molds, fiberglass molds, or even plaster molds... The design, budget, experience, number of pulls you want to achieve from the mold, type of pulls you will make from the mold all come into play when choosing the type of mold and mold material...

    There isn't a single way to do it...

  9. #9
    DIYFK member Simon1991's Avatar


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    Would this work.
    Making the desired design out of polystyrene, then doing a latex mould over it keeping it in place. Then fibreglass over the latex and pulling it off slowly when dried and use the fibreglass as the background?


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  10. #10
    DIYFK member Meep's Avatar


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    You would need to either spray wax or vaseline (my prefered method) the latex before fiberglassing so that it releases and could be peeled away from the fiberglass...

    When I do stuff like this, I heat the vaseline up to liquid then brush it on like paint...

  11. #11
    DIYFK member Simon1991's Avatar


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    Perfect thanks mate


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    DIYFK member Chasmodes's Avatar


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    Drylok won't affect the PH and will seal in your foam. You can mix cement dye for coloration and then you can apply it like coats of paint, getting the color and texture that you want. If you are carving details into the foam that you want to be seen, this is the way to go. But, Drylok also won't hide carving mistakes. Also, with Drylok, even though you don't need many coats, if you have fish that will peck at your background, some fish can scrape it off and leave you with the pink or yellow foam. It's not a big deal because it is inert, but a bit unsightly until algae grows and covers it up.

    If the foam is just a base rock and the details don't matter (in the foam cuts), then cement works well because you can mold/apply it into the shape you want. Basically, the cement covers up foam carving mistakes, and Drylok does not. But, of course, with using this method, you'd have to cure the cement properly and then do the water changes to get the pH right. I guess it depends on how soon that you'd want to set up the tank. If you have a lot of time, then either way is easy.

    I've never worked with fiberglass, but it intrigues me, because you can create just about anything. One day, I may give it a try. Meep and Dan are good inspirations!

  13. #13
    DIYFK member Meep's Avatar


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    Click here to enlarge Originally Posted by Chasmodes Click here to enlarge
    I've never worked with fiberglass, but it intrigues me, because you can create just about anything. One day, I may give it a try. Meep and Dan are good inspirations!
    It intimidated me before doing it and frustrated the heck out of me for the first few weeks, but once you find a technique the works for you (there is no one right or wrong way) and tweak the hardener to resin ratio based on temps and humidity as well as practice, practice, practice it's not all that bad... My advice is to watch every video on Youtube you can find about fiberglassing and see the different ways people do things, then keep good notes every time you use it, use digital scales and eye droppers to get consistent mix ratios and log it all in a notepad until you find what works for you... When you get all those notes done, make up a chart you can hang on the wall that says between this and that temp and between this and that humidity use this many drops of hardener to these many ounces of resin... Also, learn when it's simply not a good day to push the issue, I always aimed for sweet temps of say 70-80 degrees F as work days with moderate humidity, any hotter or cooler or high humidity I tried to avoid working with fiberglass as it was outside my comfort zone of knowing what works well for me...

    Even though I don't do it nearly as much as I used to, it's like riding a bike, once you figure it out you can pick it right back up...

  14. #14
    DIYFK member vanish's Avatar


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    If you're just building one background, I think it is hard to beat the foam and tinted drylok route. Simple. Cheap. Easy to obtain and work with materials. Mine is on year 4.

  15. #15
    DIYFK member Simon1991's Avatar


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    I live in the U.K. and itís near impossible to get hold of drylok.

    Iím wanting to make a tree trunk with roots ect and more than one as a friend wants one also.

    With fibre glass is it all fish safe or is there a certain type I should use?


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  16. #16
    DIYFK member daFrimpster's Avatar


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    I am working on a 3D background for my 150 gallon. I am using Styrofoam coated with DryLok. It is easy to work with and easy to clean up. Make certain yo buy the latex based Drylok versus the oil based drylok if you decide to give it a try. It is about $30 a gallon here in the central US. ( I just saw your post about the lack of Drylok where you live, sorry. )

  17. #17
    DIYFK member Meep's Avatar


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    Since Drylok by name isn't available to you, try and find out what other "Latex Masonry Waterproofer" are available to you, all Drylok is is a heavy duty paint that is used to seal concrete basement wall from small leaks...

    As for fiberglass, polyester or epoxy resins will both be fine as long as they are allowed to fully cure, I know the UK is all about less VOC stuff so the epoxy might be your best option even if it cost more...

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