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**CtEkM8Vq** · 07-23-2012, 06:25 AM

From the Vanadium link:

Description

Vanadium salts are naturally present in most clays used to produce white, cream and other light coloured bricks. These bricks usually give a warning by showing a yellow-green stain on their surface after they have become wet and been allowed to dry out.

Vanadium stains are not powdery crystalline deposits and cannot simply be brushed off. They are often mistaken for moss or algae which usually grows in damp areas across the whole face of the bricks and mortar joint. By contrast, vanadium stains appear on dry walls, normally as patches on the brick only.

Causes

Vanadium stains are the result of water- soluble vanadium salts. These salts are put into solution by excess water migrating through the bricks (particularly cored bricks) and brought to the surface as they dry out. During this drying-out process the water evaporates leaving the vanadium salts (and any other water soluble salts) on the brick surface. This process can occur whenever the bricks are subjected to excessive water from rain either before or (more often) during the bricklaying process. If the stains are not removed prior to cleaning with hydrochloric acid, they may turn a darker colour and be more difficult to remove.

Remedies

Method 1. Apply VanGo and leave on till the stain disappears, then wash off. This method does not require neutralising. If a white residue appears simply hose this off.

Method 2.Oxcid can be applied to the stained bricks without pre-wetting. This should be neutralised with Neutril. Do not wash off. This method cannot be used on vanadium stains which have darkened as a result of cleaning with hydrochloric acid.

Method 3 . Apply Noskum to the dry bricks. Wash off after the stain disappears and neutralising with Neutril.

Note: More water even that used during the cleaning process may induce more vanadium to the surface. If this occurs, the process may be repeated.

WARNING: These chemicals are S6 poisons and must be stored safely away from children. See warning and first aid information on individual bottle labels and on the CHEMICAL SAFETY page.

07-23-2012, 06:25 AM	#16
CtEkM8Vq Join Date Oct 2005 Posts 531 Senior Member	From the Vanadium link: Description Vanadium salts are naturally present in most clays used to produce white, cream and other light coloured bricks. These bricks usually give a warning by showing a yellow-green stain on their surface after they have become wet and been allowed to dry out. Vanadium stains are not powdery crystalline deposits and cannot simply be brushed off. They are often mistaken for moss or algae which usually grows in damp areas across the whole face of the bricks and mortar joint. By contrast, vanadium stains appear on dry walls, normally as patches on the brick only. Causes Vanadium stains are the result of water- soluble vanadium salts. These salts are put into solution by excess water migrating through the bricks (particularly cored bricks) and brought to the surface as they dry out. During this drying-out process the water evaporates leaving the vanadium salts (and any other water soluble salts) on the brick surface. This process can occur whenever the bricks are subjected to excessive water from rain either before or (more often) during the bricklaying process. If the stains are not removed prior to cleaning with hydrochloric acid, they may turn a darker colour and be more difficult to remove. Remedies Method 1. Apply VanGo and leave on till the stain disappears, then wash off. This method does not require neutralising. If a white residue appears simply hose this off. Method 2.Oxcid can be applied to the stained bricks without pre-wetting. This should be neutralised with Neutril. Do not wash off. This method cannot be used on vanadium stains which have darkened as a result of cleaning with hydrochloric acid. Method 3 . Apply Noskum to the dry bricks. Wash off after the stain disappears and neutralising with Neutril. Note: More water even that used during the cleaning process may induce more vanadium to the surface. If this occurs, the process may be repeated. WARNING: These chemicals are S6 poisons and must be stored safely away from children. See warning and first aid information on individual bottle labels and on the CHEMICAL SAFETY page.
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