Tiny Stones Embedded in Gunite

[MontyP11]

Very small stones appear embedded in the gunite only on the pool stairs. The pool has been acid washed and the stones remain. Any ideas on what they are and how to eliminate them? Thnaks

 

[kimkats]

Are you saying you have not seen them before?

You say gunite. Do you mean plaster?

If you share a picture we might be able to understand what you are dealing with.

Kim

 

[MontyP11]

Thanks for the response. Yes it is a plaster pool. They have been there for years (my brother's pool has the same thing). Most are black. Definitely not algae. I've attached an image. Thanks again.

Are you saying you have not seen them before?

You say gunite. Do you mean plaster?

If you share a picture we might be able to understand what you are dealing with.

Kim

 

[Analogbytes]

Looks like black algae to me. Have you tried scratching it several times with your finger nail?

 

[MontyP11]

Thanks for the response. Definitely not algae. This has been around for years even after an acid wash, bleach wash and power wash. Just recently I used a 3500 psi pressure washer and no change. Will not scratch off either.

 

[kimkats]

Can you feel them?

Kim

 

[MontyP11]

Completely smooth. Almost like it is part of the original plaster. Strange thing is that my brother has the exact same situation and they were different pool builders.

 

[kimkats]

Were the pools built about the same time? Do you have any idea if the plaster people were the same? Many PB use the same subs.

Kim

 

[gwegan]

Just looks like black algae to me.

Your plaster looks old? How old?

They may have been in the original plaster and creamed and troweled over. Now that the plaster has gotten older and the water has slowly eaten away the cream you see these. Its on the edge of the steps but not elsewhere in the pool?

I suspect your plaster coat is thinner there.