Care and installation...
When installing heavy stone, marble or cast iron ornament it is highly recommendable to build permanent concrete footings to a minimum of 15cm./6" for the objects to sit on. This prevents contact with the freezing ground in winter and also provides stability - some vases on stands can end up leaning at alarming angles if placed on soft ground.
When deciding on where to site items it is worth considering the impact that the elements can have on an item of ornament. Nothing is impervious to the passage of time and the elements so a little thought as to what may be the most advantageous as well as damaging conditions will be well spent. In general frost and ice are the most damaging, but wind blown particles can also damage pieces. Trees will weather objects very quickly, the sap and leaves that drop from them is the ideal base for algae and lichen to grow on, by protecting items from the wind it can often be wetter under the tree meaning objects are at risk for longer. It is worth noting that bird droppings can be damaging, especially to marble as can some tree saps. High winds can also send branches flying.
Covering garden ornaments
Extreme winter weather can be damaging to garden ornament - acid rain, snow and ice can affect all materials, especially the more porous. In more Northern climates, it is worth covering up ornament, especially marble, for the winter period. It is important to do this correctly as wrapping something badly could cause more harm than it prevents.
As a general rule remember that air needs to circulate and the aim is to avoid condensation forming as this can freeze on the object negating the good practice of wrapping. The use of a breathable membrane and not ordinary plastic sheeting is recommended. The best solution is to wrap items and then to place wooden “sentry boxes” over them. This adds further protection from a surprisingly common problem of statues etc, being hit by falling branches in high winds.
Cast iron
Cast iron becomes brittle with age and this is exacerbated by freezing temperatures. Never drag cast iron seats to move them - the legs snap off surprisingly easily. Always lift them with adequate support to stop them flexing and snapping.
Cast iron is normally painted and the painted surfaces will inevitably deteriorate with time. The porosity of cast iron makes it virtually impossible to escape problems with rust. If these are superficial, simply wire brush over the problem area and apply a rust inhibiting primer (zinc or red oxide). Then recoat with the exterior metal paint colour of your choice. One of the most common questions to be asked is what colour should an object be painted, to this there is no right answer, taste is personal. The main foundries offered items in brown, green, white and bronzed. Usually also adding that special colours could be arranged if required. You can help repel the moisture which causes rust by also waxing the surface of cast iron ornament. This needs regular reapplication to have any lasting effect and must be done when the object is completely dry so as not to seal in any moisture
If the painted surface or the actual metal surface is very distressed (beyond what some may consider an attractive antique look) then consult a professional restorer. Cast iron can be taken back to its original surface which can often reveal a previously hidden degree of cast detail. The likelihood of rust reoccurring is much reduced if this is done as all traces of it are initially removed , rather than just its surface manifestation.
Terracotta
Terracotta as opposed to stoneware, which is fired to a higher temperature is susceptible to weather damage as it is extremely porous. Planters can crack in heavy frosts. Make sure that there are drainage holes in the bottom and it is worth mixing small pieces of polystyrene in with the earth since when the earth freezes and expands it will crush the polystyrene rather than cracking the pot. If terracotta has become friable and is crumbling due to frost damage, consult a restorer. It is possible to consolidate the surface and make good.
Stone / Marble / Composite stone
All are porous and subject to potential weather damage. A build up of green algae and lichens is to be expected , and on carved and composition stone will form an attractive patina. Some composition pieces have an internal iron armature and over a long period of time can deteriorate when the armature becomes rusty as it expands, cracking the stone around it. Most people consider that marble looks better if kept clean. It can be washed off by gently scrubbing with warm water. If more serious, especially if lichen has been given time to grow, always consult a restorer. The lichen roots into the object (visible as little black specks when cleaning marble).
Pollution can also cause patches of black staining in the undercut parts of marble statuary – If desired this can be removed but it needs to be done professionally.
Power hoses can be used but only with extreme caution - used at the wrong distance, and on an object which may have weathered more than is apparent, it can simply blast off the material to be cleaned (eg fingers on statues). NEVER use bleach or any caustic cleaning substance.
All these materials show weathering by becoming friable . Marble becomes sugary in texture and in turn becomes even more porous, and thus even more exposed to damage. It is important to protect the surface and consolidate if there are any cracks - this should be done by professional restorers.
Cracks in any material will be made worse by freezing/thawing and could break apart the object.
Lead / bronze
These both acquire an attractive patina with age but also need protecting in winter. The effect of verdigris which turns any brown patinated bronze figure green with time is to be expected. The surface can be enhanced and protected by the application of wax - only when completely dry. Lead like composition stone can suffer from the rusting of internal steel armatures - look out for splitting, bulging and signs of rust and consult a restorer if found.
Rust staining
Rust staining is notoriously difficult and sometimes impossible to fully remove. More alarmingly it can be a sign of problems in materials like marble and stone. Often old repairs have been carried out where steel pins have been used to attach broken elements, for example a head to a marble figure. Over time the steel pin has rusted internally. The rust staining is a sign of this rust having leached through the porous material. In time the expansion caused by the rust will break the head off again. Rusting repairs of this sort should be removed by a professional restorer and re-done using stainless steel.