Lead’s unmistakeable natural patina is a distinctive mark of quality, particularly in heritage settings.
Lead is also one of the longest lasting of planter materials, and its high malleability allows for intricate surface design.
IOTA’s planters are manufactured from 3.0mm lead sheet clad onto 3.0mm stainless steel. The resulting double-skin planters deliver the unique aesthetic of lead, whilst relying on the superior strength and stiffness of steel for the planters’ technical performance. IOTA’s lead-clad planters are stronger and lighter, and can be made larger, than would be the case with a solid cast lead planter.
IOTA’s lead planters are clad in architectural-grade lead sheet, which contains a minimum 99.9% pure lead, with trace amounts of copper and tin carefully controlled to improve stability.
The inner stainless steel planters are fully-welded and faired, and fabricated to the highest standards. Although these planters will not be seen, their structural integrity is central to the longevity of the final lead-clad planters.
The architectural-grade lead sheet is bonded to the inner stainless steel planters using industrial contact adhesives. These adhesives not only create an extremely robust and long-lasting bond, but their flexibility is also necessary to mitigate the differential thermal expansion rates of the two metals.
All of the edges and corners of the lead sheet are then welded, using a highly specialised process traditionally and commercially known as "lead burning”; which uses a high-temperature torch to melt the edges of the lead sheets together, fusing them into a single, contiguous piece of metal. Finally the finished planters are expertly patinated by hand.
The key benefits of true lead sheet are:
Lead is extremely expensive so it is only ever specified for high-end schemes.
Lead planters are the definitive ‘gold standard’ mark of quality, and they feature in hotel courtyards, and street level reception / drop-off zones for the finest hotels.
Generally-speaking, lead would never be specified for unprotected public realm. The cost would be prohibitive, and the soft lead sheet on the planters could be too easily ‘stripped’ for melting down. However lead is perfectly suited for protected public spaces, such as secured public museum gardens.
IOTA’s design methodology delivers a lead-clad planter at much less weight than a comparable cast lead planter option.
Even so, IOTA’s lead clad planters are very heavy. As a guide, a standard L / W 1200 x H 1000mm tree planter in 3.0mm powder coated steel might be around 160kg, but the same size lead-clad planter would be around 370kg. And these are the empty weights, not allowing for growing medium, water, trees etc. So any specification for lead-clad planters must take full account of this issue – in terms of delivery and installation logistics, and the near impossibility of being able to move the planters once filled. On the flipside, however, lead-clad planters are extremely stable as tree planters, for example in high windage locations.
Lead is toxic, and this toxicity can leach into planters and affect plant development [and lead planters should never be used to grow herbs or vegetables for human consumption]. This is another benefit of IOTA’s construction methodology, as only the stainless steel inner planter comes into contact with the growing medium, not the lead cladding.
In highly corrosive, industrial, or coastal environments with moderate to high salinity, unprotected lead can degrade.
Airborne sea salt and spray contain high levels of chloride ions. These chlorides combine with the surface lead to form soluble compounds like lead chloride. Instead of building a protective shield, this layer dissolves and continuously exposes fresh metal to moisture and oxygen.
Given lead’s high cost – and thus the commensurate expectation of longevity – lead-clad planters are not recommended for coastal locations.
Speak to IOTA about the potential benefits of Lead for your specific project.
