Gold and Metal Leaf Part 1 - What's What and How do I Specify?

We apply gold leaf, silver leaf and a range of other metal leaves in a wide variety of styles, shades, carats and weight.
Often there is confusion between the different types of materials and the benefits and risks associated with each. Particularly for those specifying the material I felt it was important that they have a better grasp of the material and some time back put together a description for Interior Designers, Architects and Specifiers we work with. I had the need to go and drag it out again for a customer and realised it was possibly a blog post....or even two. So here is part one and I have added to this by doing a second part which is all about the best application methods and that I'll post in the next few days. This is a HUGE subject and I could have written a lot more but I've tried to keep it a manageable amount of information

Gilded dome using 24ct in the Middle East - this was a huge project that the Carte Blanche team played a
small part in.

Gold and Silver Leaf

•    Genuine gold leaf is 85mm X 85mm There are 25 leaves in a book and this will cover 0.18 square metres with no waste. We allow about 7 books per sq metre depending on the type of surface we are applying it to
•    Genuine silver is 95mm X 95mm
There are 25 leaves in a book and this will cover 0.22 sq metres with no waste. We allow about 6 books per sq metre depending on the type of surface we are applying it to
Gold leaf comes in various colours and carats. As a rule of thumb the higher the carat the less likely it is to tarnish. The different carats also are to do with colour. All gold is cut with another metal – despite what you will read on the internet, even 24ct has the tiniest amount of another metal (usually silver) in it to make it malleable enough to use. Correctly applied, high carat gold will normally last longer than the substrate that it is applied to.
To produce a wide variety of colours, copper and silver is mixed with gold. When copper is added, the leaf becomes warmer and richer in tone. When silver is added, the leaf becomes paler in tone. The addition of these other metals lowers the carat value of gold leaf. Gold leaf is manufactured in a range from 9ct "White" to 24ct. Gold is completely resistant to corrosion. The addition of silver and copper lowers the resistance of gold leaf to oxidisation. However, the copper or silver in 23.75ct or 23ct leaf is so low that it will maintain its integrity outdoors for 30 years or more. Carats less than 23 are recommended for indoor use only and many colours and carats are available. We carry colour charts to help you determine the right tone for your project.

A winged lion holding a Bible is known as a Lion of St Mark - these two once graced the Savoy before it's refit.
They were bought at auction in very poor repair. We gilded them in Palladium Leaf.

Silver leaf is very prone to tarnishing and so we seldom recommend using it in architectural gilding – our recommendation is to use Palladium, Caplain, Platinum or Aluminium

There are 3 types of leaf in the "gold leaf" category that aren’t gold and none of them tarnish readily – Palladium, Caplain and Platinum. However it must be noted that be care should be taken using palladium (and therefore also Caplain) in a chlorine rich environment (a swimming pool or fountain. etc.) as the chlorine will cause the palladium to turn. once again I'd like to thank Michael Kramer for this information which he gave in the comments below.
Palladium is a base metal that is similar to Platinum but a slightly warmer look than Platinum. It is good substitute for silver but offering a slightly different tone, like a silver with a slight gun metal undertone. Caplain leaf is a combination of palladium and gold so just a slightly warmer cool tone. Platinum…well that’s platinum, with a suitably platinum price tag to go with it!!!

Copper Leaf Wall - this installation is being finished off by Gibson removing the last of the "skewings"

Metal Leaf
Also known as Schlag, Brass Leaf and Composite Leaf
Metal Leaf comes in 3 colours – Gold, Copper and Aluminium
•    Metal leaf comes in sheets 14cm x 14cm. There are 25 leaves in a book and this will cover 0.49 square metres with no waste. We allow about 2.5 books per sq metre depending on the type of surface we are applying it to
Both Copper and Gold Metal Leaf tend to tarnish Copper being the most risky. Reducing the risk of this tarnishing relies on a number of factors – most are to do with product knowledge and strict good practice but there are no guarantees with it. The reduced cost comes with a risk, like so many things in life. 

Patinated Aluminium Leaf

Aluminium leaf on the other hand seldom tarnishes - as pointed out by Michael Kramer in the comments below - it can tarnish if it is in a salt air environment (along the sea shore, a port city, etc.) and there is high humidity. This makes it an excellent alternative to Silver Leaf, although the larger size of the squares does give the knowledgeable person the hint that it isn’t silver if you are installing a gridded wall or ceiling

Reducing Risk of Tarnishing
Here are the things we do to reduce the risk when using metals that tarnish 
1.    Great care is taken in the preparation of the surface to ensure it is sealed as many oxidants can come from the back of the leaf - thanks to Marlow Demars for reminding me in the comments below of the importance of this. If we are not doing the preparation we supply a comprehensive specification for the decoration of the substrate prior to the leaf being applied.
2.    We insist on a strict site conditions – there are a number of atmospheric site conditions that can affect the metal. These are mainly chemical; glues, solvents, acids and alkalis used in the area can affect the metal.
3.    The substrate must be scrupulously clean as must the tools used.
4.    Great care is used not to touch the leaf and leave acid from the skin on the surface.
5.    Knowing the correct combination of products to use for each leaf to minimise contamination is vital.
6.    Sealing the leaf with the correct material

I hope this is a useful post - do ask questions if I've missed anything I'd be delighted to help.
If you'd be interested in finding out more about the costs of having gilding carried out in your home or business premises, please don't hesitate to give us a call 
01738 587600 and speak to Cait or Gibson