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Causing calcification of knitting canvas (LLDPE mesh)

  1. Apr 29, 2015 #1
    I know this sounds like an odd question, but to me, it would be useful to figure this out, so I'm throwing this out there to see if it bounces off anyone.

    I would like to know if there is a relatively simple way to cause calcification of a sheet of knitting canvas. The material in question is Darice #7 mesh (LLDPE), which you can get at any fabric store or wally world.

    My reasoning for wanting this is related to an aquarium filtration system, mainly used in reef aquariums, that grows algae on a substrate for purposes of nutrient reduction. Right now, the standby material is the #7 canvas, which is vigorously roughed up with a hole saw or saw blade so that it is really prickly. The idea being that this 1) reduces the smoothness of the surface of the canvas, allowing algae to adhere faster and 2) gives a greater surface area for the algae to anchor on to.

    But in my experience, the thing that causes algae to really get a foothold is calcification of the screen. This happens over time, so I purport that initially, the roughing-up will probably help algae adhere, but if over time this matters less and less, because as calcium adheres to the screen, this creates a microscopically rough surface that, even if disturbed from scraping off algae or scrubbing with a stiff brush, will allow for rapid regrowth of algae. For reference, the algae is removed from the growth substrate on a regular basis (7-14 days).

    My goal is to figure out how to start with a calcified screen so that I don't have to wait 2 months for that to happen naturally.

    I'm thinking that I could just take a wire brush to scuff up the material and get rid of the smooth surface, then place the screen in something for a period of time that would cause the calcium to deposit on to the screen.

    I'm also assuming that it is calcification that is the key here. I haven't had a "mature" growth substrate analyzed or anything, it just seems to make sense.

    Also I'm not opposed to using another material for the substrate, but it's gotta be "reef safe" material.
     
  2. jcsd
  3. Apr 29, 2015 #2

    Borek

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    Staff: Mentor

    The only approach I can think of at the moment is to leave the material covered with a thin layer of some solution to dry out. The solution must contain calcium ions and something that wouldn't be unsafe for the reef chemistry. Unfortunately, calcium carbonate is weakly soluble, so there is no way to prepare its solution of a reasonably high concentration. Perhaps start with dry CaO, add some water and leave everything in a CO2 rich place? Later rinsing will wash out hydroxide, so the final product should be safe.

    That's just me thinking aloud.
     
  4. Apr 29, 2015 #3
    A commonly used dosing mixture is Kalkwasser, basically pickling lime, something like that? Could make kalk paste and place it in that. But I guess would something like that actually be so caustic (in paste form) as to dissolve the screen material itself?
     
  5. Apr 29, 2015 #4

    Borek

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    Staff: Mentor

    In general polyethylene is base resistant. Besides, even if its surface gets slightly etched, that's good - it won't be that smooth.
     
  6. May 31, 2015 #5
    I have another possible route I could go with this. Instead of causing a layer of calcium to build up on the mesh, what about this:

    Dip the screen in something that would cause the material to soften
    Remove the screen when it gets to the point of surface softness, but is still firm enough to maintain it's default shape (mesh)
    Lay the screen in a tray full of fine quartz sand (like pool filter sand) and pour sand over the top, and press in
    Allow "softened" screen material to re-solidify

    The idea being that the screen would now be "impregnated" with sand on the surface that would not easily be brushed or scrubbed off

    I tried doing this by heating up the screen, but the point at which the screen gets warn enough to allow for this to occur is also the point at which the screen turns into mush. So then the question is, what would do this? I'm guessing that it would be something nasty like toluene or xylene...hoping for another answer, one that is not quite so dangerous...
     
  7. Jun 1, 2015 #6

    Borek

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    Staff: Mentor

    I am not aware of any cheap and safe solvents that could do the job.
     
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