Calcium issue in Grotto to become scifair project?

[letabahall]

Our chlorinated pool just turned one this month. We have a grotto that has large white almost stalactite looking crystals growing on the roof and sides. The grotto is made up of Moss rock. I have always just assumed that it is calcium. I know NOTHING about chemistry but between my husband and I we have kept all the levels correct and compensated immediately when a level started showing signs of straying from the norm. I am amazed at how large these 'crystal' looking spots have gotten in just one year.
My 11 yr old daughter is starting on the science magnet program next week at intermediate school. This school has a lot of very sophisticated science students because our district is the NASA district and parents put a lot into their children's education. My daughter has been looking for science fair projects for 3 months now and keeps running into the 'real world application' problem of any idea she presents.
Chemists/Mineral geeks out there, if you are willing, please tell us how to test for what those deposits are. My daughter was thinking about either investigating which conditions are present to cause this excessive crystal formation (if that's what it is) OR which would be the most environmentally friendly method of cleaning the desposits. We have left the deposits growing, untouched, mostly due to fascination from the kids, so we have a prime experimental ground.
Any help, ideas, would be much appreciated. Please bear in my that I am a software engineer and my husband is an instrument technician.. our combined chemistry knowledge is probably equivalent to first year college :-(
Thanks! I will take pictures tomorrow and post...I personally think the deposits are spectacular despite the fact that they look like bird poop from a distance.

 

[Shane1]

You have came to the right place to figure out what they are and how to get rid of them. I would love to see the pics and your pool in general. Hopefully it isnt mold or something like that.
Welcome to the site!

 

[JasonLion]

Welcome to TFP!

They are almost certainly mostly calcium, but there are likely to be a whole variety of impurities, salt, dirt, etc in the calcium. You can test for calcium by putting a few drops of muriatic acid on one of the crystals. If there is calcium the acid will foam up.

 

[heather.wallace]

CCISD?

To test for calcium, you can also use vinegar (safer than muriatic acid). I'd also dissolve the unknown in distilled water and test the resulting pH. (Don't use a pool test kit for this, use Universal pH paper or a pH probe....if CCISD, you can borrow a GLX pH probe from any of the schools. Also use a microscope to look at the shape of the crystals. Daughter can bring crystals up to a high school and may be able to take digital pictures to put in her lab notebook/board. Another piece of data to collect is to dissolve the unknown in distilled water and test using a conductivity meter (operated with a 9 Volt battery) - just borrow it from a school.

Another thing I'd do is take some unknown....dissolve in distilled water..... and take it to a pool supply for free testing. (This may be cheating a little, but you can use the info to compare to your results.)

If possible, you can also do a "flame test" and use a spectroscope (basic supplies found at the schools which include a bunsen burner and spectroscope) to record the color flame that the unknown gives off. The spectroscope will "break down" the color of light to individual wavelengths and be able to support the other evidence for the presence of calcium.

I'm not sure if you have a chlorine puck, salt pool, or if you use the BBB method which includes baking soda - because both salt and baking soda contain sodium which could also be a culprit. Do you have borates? Could the sodium (from sodium bicarbonate/borates) and the chlorine (from bleach) combine to create a salt that has precipitated out in some areas??? Hmmm. Another possibility is the natural effervescence of the moss rocks or the grout product the pool-builder used.

Whatever your daughter chooses, be sure she keeps track of EVERYTHING in the log book - even if it's not going to be a part of her "final" design. The point is that the log book tracks her thought process - including her decision of what the experiment will even be.

On a side note - If wanting to do an experiment with the pool, I like the "what conditions grow these?" - because it would be applicable to me as a pool owner. I don't want to spend the time/$$$ cleaning them up!!! Remember though...when designing her experiment she will need to have a control. Depending on what her experiment is this might create some difficulty.

If you are brainstorming other pool related experiments, she could compare how temperature affects chlorine loss....or if you have access to some weather databases, she could collect daily sun/UV exposure. (Remember, not all the data has to be collected/measured by her....it just has to be analyzed by her.) ....She could ask how the UV exposure changes the water temp (and therefore chlorine consumption, etc.) Or...is it better to run the pumps during the day or night?

Any experiment that would give you reason to save $$$ (and time - think of marketing the conclusion to pool service companies) would be the real-world relevance.

Feel free to contact me if you need more help - I'm the science specialist at Springs.

 

[letabahall]

[attachment=0:2nsf9olt]DSC02056.JPG[/attachment:2nsf9olt] Calcium deposits in our pool. Is this limescale? Is this caused by carbonic acid in the pool reacting with ions in the rock? Howcome its mostly where the cement joins are?

 

[letabahall]

Thanks again everyone for your help. My little girl is still debating this idea...and I think she may be onto something. The idea has to do with global warming. She watched a video of 'global warming in a bottle' and how if you had a control bottle with nothing but air in it, then pumped C02 into the experiment bottle, and heated both up with a heat lamp for a few hours, the C02 bottle would take longer to cool down. She said, what if we put a moss rock and water in a bottle and then pump Co2 into it and just leave it for about 2 weeks. Will the Co2 cause the calcium to grow? (alternatively, will it make the water harder) faster than the normal air with water and moss rock (all sealed in bottles). I thought we would have to have 4 bottles, one with just air and water, one with air mossrock and water... that would be the control... to show that we are getting the global warming effect temperature wise as compared with the other 2 bottles...one with C02 and water... one with C02 water and moss rock... Does this make sense to anyone? Surely if excess CO2 is in the air, it will be absorbed into the water and combined with the global warming effect, will cause increased carbonic acid reaction rates. Oh FIDDLESTICKS why did I become a software engineer; my daughter needs a chemist, or a zoologist. Her alternative idea is to build an algae bioreactor and see if algae grows better with red LED or blue LED (idea from youtube). I prefer the mossrock idea because as far as I can tell, its an original idea. First week of science magnet school and she has already spent the entire weekend on homework... but science is her passion so she had fun.

 

[heather.wallace]

Go with moss rock. Much cooler and original.

 

[harrisjc]

To me this looks like efflorescence http://en.wikipedia.org/wiki/Efflorescence. What really caught my eye is not the big splotch in the middle but the white stuff coming out of the edge of the grout in the upper right corner.

I see a lot of this white stuff on the edge of my grout on my pool. What I've figured out is happening on my pool is that the thinset under the tile and grout is experiencing efflorescence. It either comes to the surface through the grout or more easily (and noticeable) through a minor separation between the grout and tile on the edge of the grout. And to me that looks like what is happening in the upper right corner of your picture. Something underneath may be experiencing efflorescence. The big splotch in the middle may be an area where it is easiest for it to surface.

If the white stuff is fairly easy to scrub/brush away then it fits the bill even better. (as opposed to really scrubbing and chipping scale off)

My pool is two years old and was doing it worse in the first year. Unfortunately, after researching this, I don't have a good answer to the problem. I do know that there is a limit to the amount of stuff that can be extracted from the underlying thinset. So, it will stop eventually.

http://www.johnbridge.com/ is a tile/grout forum where they do have some ideas about mitigation.

 

[anonapersona]

I just found what may be the answer for both of you. I was talking to a Stone company about sealing the pool waterfall and the discussion turned to the calcium deposits on the pool rocks. She said that it may be efforescence and that it is cleaned with pressure washing, perhaps some chemicals if that was not sufficient, then the rocks are sealed. Once the water is not moving through the rocks, or grout, the deposits that appear on the surface will not come back.

So, sealing the surface is the key, once the growths are removed.

 

[harrisjc]

Thanks. That is good info. I haven't been able to really clean the stuff completely off. Good to know about pressure washing. The sealing makes total sense since it is the water that flowing through the thinset that allows the efflorescence to happen.