How do you know if stucco is lime based?

[Sam1234]

Last year we bought a period property (circa 1700) to which a brick façade was added during the Victorian era. The top of the façade is crowned with decorative stucco, and so is the base (for 10 foot or so), both white and in need of freshening up.

I am not sure if the stucco is lime based or made from modern concrete.

So as I am not sure what the stucco is made of can I just apply a silica based paint?? It has not been painted with plastic / acrylic paint to my knowledge. .

The surface is sound structurally. It would seem that you can apply silica based paint to anything, be it lime rendered or not.

Would be grateful for some advice!

 

[LadyArowana]

Just bumping this up. There are some threads here about testing the difference between lime and cement,
http://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=14339 and
http://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=14321

 

[Keithj]

The test I've always used is to drop a little bit in vinegar. If it fizzes, it's lime. If it just sinks, it's concrete.

 

[LadyArowana]

The test I've always used is to drop a little bit in vinegar. If it fizzes, it's lime. If it just sinks, it's concrete.

... or possibly something I cooked.

 

[paulb33]

Our lime guy said cement will fizz too....

 

[LadyArowana]

Our lime guy said cement will fizz too....

He's putting it in Coke isn't he. :lol:

 

[Zebra]

and I put a bit of very old lime in vinegar and it just sat there, emitting only the feeblest of bubbles

 

[livias]

As you will have gathered by now there is no simple test to distinguish lime from cement based mortar, mostly because they are so similar. However, cement mortar tends to be more hard and brittle and SNAP when you break it. Lime mortar is more likely to delaminate and crumble at the edges. In general, exterior plaster was lime based before the 2nd world war, cement based afterwards though there are always exceptions. Cement was invented c1820 though it was much weaker in the early days than it is now and so much more like lime.

I don't know anything much about silica paint and I would be cautious about using it, mostly because once painted you can't undo it. How about painting some sample areas in an inconspicuous spot with silica, limewash and "limewash with additives to let it cope with cement"*** see how they fare and and consider the situation for a year or two

*** Which I suppose could just possibly be silica paint ...