Brown blobs on raj green sandstone

[bodgeitandscarper]

Ive got brown blobs on my paving laid about 5m2 , ive phoned the stone supplier and they said its " ironisation " (made this up, obviously) but not had this problem before and most are affected, and ive got another 35m2 in crate to look through. What should i do ? Carry on ? I understand you can get small bits of iron in paving but this paving looks dirty!

[Old Codger]

Ive got brown blobs on my paving laid about 5m2 , ive phoned the stone supplier and they said its " ironisation " (made this up, obviously) but not had this problem before and most are affected, and ive got another 35m2 in crate to look through. What should i do ? Carry on ? I understand you can get small bits of iron in paving but this paving looks dirty!

are the brown blobs on the unlaid slabs or only on the ones you've laid?

[Tony McC]

They probably mean "iron mineralisation", Ionisation is a completely different process and doesn't really affect stone paving.

Iron mineralisation occurs when concentrations of iron-bearing minerals that have been buried in the rock for millions of years are suddenly exposed to the cool and damp atmosphere of a British or Irish garden. The iron minerals oxidise, which is a posh way of saying they rust.

These 'concentrations' are often quite small, not even as big as the head of a match, but once the 'rusting' starts, it spreads and covers an area 10, 20, even a 100 times as big, effectively staining the stone in the process.

As the global appetite for cheap imported asian stone has grown exponentially over recent years, the top-quality rock beds with very little iron mineral content have been used up and we are faced with more and more stone that has more and more iron content. When it comes to the 'bargain' stone offered by some suppliers, this higher-than-usual iron content is part of the reason why the stone was so cheap (relatively speaking).

The consequence of all this is that the suppliers will tell you that the iron staining is a 'natural process' and as such, they can't be held liable. It's akin to the variation in colour or texture of the stone. It's part of the stone and you just have to accept that. The better suppliers will sometimes offer to swap out any flags that are really badly affected by oxidising iron, but they do so as a gesture of goodwill, not because they are legally obliged.

The good news is that there are a handful of products that will 'wash away' the oxidation: Weiss RCI and Lithofin Bero are both very good at shifting even stubborn iron stains. However, they will only shift what is evident at the time of treatment. There may be other, hidden concentrations of iron mionerals that will only become exposed as the stone weathers, and so you may find that new rust spots appear every so often as previously buried 'spots' are revealed to our soggy atmosphere.

Note that it's important to treat *all* of the affected flagstone, not just the spots. Treating just isolated spots can result in 'bleaching', where a noticeably paler patch of stone replaces what was previously a rust stain. Iron at much lower concentrations may be present throughout the stone, so you need to treat the whole flagstone to ensure and even result.

[bodgeitandscarper]

Thanks for this info Tony, I contacted Cowley stone and they said exactly that " its a natural process". They also said i could buy some Lithofin Bero at my expense .

[Tony McC]

To be fair to Cowley Stone, they are one of the better suppliers I mentioned and, if Scott thought it really was a bad batch of stone rather than just 'typical' mineralisation,. he'd swap them for you.

Try the Bero - it's not expensive (relatively speaking) but it does tend to resolve over 90% of such problems.

Let us know how you get on......