mastic specification for tank building

Discussion in 'Hardware & DIY' started by danmil3s, 16 Mar 2019.

  1. danmil3s

    danmil3s Member

    Messages:
    725
    hi guys,

    been a long time since i posted gave up for a bit but having more success now :)
    IMG_20190316_201502.jpg

    Does anyone have any experience building tanks? is there a ratio between glass thickness/ tank size to achieve minimalist mastic my current mastic looks like bellow and i'm moving/revamping the tank so am considering redoing the silicone work.
    IMG_20190316_200557.jpg


    thanks guys
     
  2. Geoffrey Rea

    Geoffrey Rea Member

    Messages:
    211
    Location:
    Cambridgeshire
    5 minutes 50 seconds in:

     
  3. zozo

    zozo Member

    Messages:
    6,313
    Location:
    Netherlands
    In theory there probably is, since the tech data sheet provides data in strengt propperty of the silicone, likely in Newton / mm and elasticity in % etc.
    One could calculate the minimum amount required, since we know the water volume and pressure working on it. But this is a rather extensive calculation only required for rather large projects.

    For any standard sized household aqaurium the glass thicknes versus volume only is calculated in this safety factor the silicone strenght will always exceed the glass strenght and there for is neglectable. Depending on the manufacturer even in filling gaps up to 10mm the silicone is stronger than the glass it holds together.

    Since the safety factor is in the glass thickness the silicone glass to glass connection gives sufficient structural strenght to hold the tank together under pressure. the corner seam is purely an extra seal to prevent leakes on the long run and has no structural strenght purpose. You can often see this in standard sized factury made aqauriums using pressurized automated silicone guns applying a calculated amount, they don't even bother to smooth out and flatten the inside corner seam in the tank. It's just a small rounded bulge of silicone pressed out during asessambly and left to dry. Only when it comes to very large tanks, than a lot more attention is given to this detail. But anything standard in stock over 100cm i don't believe excist, for bigger you need to do a custom order.

    Thus you can make it as minimalistic as you like.. :) The thing is and that is tricky with silicone.. Working minimalistic requires perfection in cleanliness.
    The glass needs to be 100% clean, for example making a 1mm seam than a 0,5 mm dirty spot will damage 50% of the seams integrity. :)

    For a new build with new glass this is not that much of an issue.. But when it comes to resealing, you need to cut out old silicone.. And that is a pain in the neck, removing silicone and leave a perfect spotless clean surface behind after that is extrmely difficult. Glass can look clean to the eye, but once new silicone is applied you see the small inconsistencies pop up in contrast like sour thumbs.

    The task resealing isn't difficult, as the video shows it's a straight foreward childs job.. But doing it perfectly clean on old glass is.

    If minimalistic easthetics is the goal i personaly would reconsider a new build with new unused glass.
     
    Last edited: 17 Mar 2019
    Edvet likes this.
  4. danmil3s

    danmil3s Member

    Messages:
    725
    Thanks for the video Geoffrey. I was hoping to go for clean lines and not have the overlap . The tape isn’t a bad idea but I have some proper tools for creating tidy joints.

    Thank you for your thoughts Zozo the tank i want to re mastic is a 7 footer so a large home aquarium. i don't really want to spend the money on new glass as that ends up being very costly. I'm not worried about the thickness of the joint I've just noticed that on larger tanks it seems to be thicker between the glass so i didn't want to under do or over do it if that's possible. minimalistic was probably the wrong choice of words tidy would have been better. I'd just like to do away with the "rounding" at edges on at least the front pane. The tank has been filed for 8/9 years now and was 3rd hand when i got it. i might just clean it up?if i do redo the mastic I’ll probably just go 2mm in case there is a bit of dirt that might compromise the joint.
     
    Geoffrey Rea and zozo like this.
  5. zozo

    zozo Member

    Messages:
    6,313
    Location:
    Netherlands
    It can be done it aint hard.. But you can forget about silicone removers, that is a waste of money.. Fully cured silicone can not be disolved and can only be mechanicaly removed.

    Depending on the glass quality and the agresiviness of the silicone used in the past (Because its acid based silicone) it might have stained (etched) the glass over time. That makes it very difficult to see difference between not clean or etched staines that can not be removed. Also scratches in the glass are impossible to propperly clean out.

    Not clean means silicone doesn not adhere to the glass.. And glass can look or feel clean, but after new silicone is applied you will notice spots that where not clean enough showing with a different color or an airbubble forming where the kit doesn't want to adhere.

    This you will only see after you're done applying the silicone. Anyway you are definitively at risk making it look worse that it already is. It's taking your chances and hope for the best..

    Good luck.. :thumbup:

    Ps. That are the scenarios all those genious diy videos do not show.. They never come back with an update how it looks after a few weks or months use again.
     
    Last edited: 17 Mar 2019
  6. danmil3s

    danmil3s Member

    Messages:
    725
    thanks Zozo you've put me right off now :lol:. think i'll just clean it up.
     
  7. Geoffrey Rea

    Geoffrey Rea Member

    Messages:
    211
    Location:
    Cambridgeshire
    Yep.
     
    danmil3s likes this.

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