Every work executed in "mixed" or non-traditional media has many specific peculiarities, and on that ground requires careful studying and an individual method of approach to the method of conservation and preservation. As with all media, maintaining a safe and stable environment is crucial. Ensuring proper light, humidity, and temperature conditions remains paramount for mixed media works.

The conservation of mixed media objects (for example, a sculpture that combines paper, oil paints, and glass) and mixed mediums (for example, metal alloys) is complex due to their composite nature. In general, each media should be treated according to the methods summarized in the other sections, and the work as a whole should be displayed and stored properly. As a general rule, the dominant medium should dictate the specific manner in which the work is displayed or stored, with modifications where necessary due to the other media in the work. If, for example, the work is a large photograph that has oil paints applied in some areas and objects collaged onto the surface, the work should be displayed and stored in a manner that protects all three media, and if the work requires conservation, then each media will have to be treated separately but with knowledge of how the piece fits together, so as not to damage another part in the process.

Modern and contemporary art in particular often makes use of alternative and mixed media. It is important to understand what exactly the various media are and the best way to care for each one. Conservationists suggest creating a “conservation plan” for a mixed media work, in which a trained professional studies each medium and material in the work and the way in which the various media join together in order to come up with a personalized display and storage method, as well as how any repairs will be conducted, should the need arise.

PAPER COLLAGE
A collage (From the French: coller, to glue) is a work of formal art, primarily in the visual arts, made from an assemblage of different forms, thus creating a new whole. A collage may include newspaper clippings, ribbons and other textiles, bits of colored or hand-made papers, portions of other artwork, photographs and other found objects, glued to a piece of paper or canvas. The origins of collage can be traced back hundreds of years, but this technique made a dramatic reappearance in the early 20th century as an art form of novelty.
Knowing and understanding how the collage has been put together (what type of glue or adhesive has been used to attach the paper to the support) as well as the particular characteristics of the papers used (for example, tissue paper and newspaper are especially susceptible to decay) will determine how the collage can be preserved as well as repaired if necessary.
When talking about conservation of paper collage, maintaining a stable environment is paramount. Works on paper can easily be damaged from too much humidity (in which case mold spores can grow) or too dry/hot conditions (in which case the paper can become brittle and flakey.) Paper collage should be stored in acid-free containers in a stable environment, where there are no extremes in temperature and humidity.
To protect displayed works from dirt, dust, and handling while maintaining a controlled setting, they should be mounted properly and protected behind glass-- the work should never rest directly on the glass, however. It should be properly matted and attached to a support of Japanese rice paper using a wheat or rice starch paste-- using tape can cause rips and tears. Dry mounting, in which the entire work is pasted to the back support, is irreversible and should not be used when framing expensive works. The framing process should be done by a professional when the work is of higher value.
In addition to mixed or alternative media pieces, a work can also be made of one material that is itself a combination of several materials. The most common example of this type is metal alloys. Listed below are the most common metal alloys and the basics of how to preserve and care for each.

LEAD
The production of lead sculpture reached its height during the 18th century. Most was cast in one piece, and sand or plaster used as a core material. The iron armature was left inside sculptures to provide support. They were frequently painted with lead-rich oil-based paints.
The original iron armature will inevitably corrode, as it does so the rust builds up on the iron. Thus lead sculpture is particularly vulnerable to splitting and collapse as the armature is weakened. However, lead itself is generally resistant to corrosion and if unpainted, the surface will develop a prized, protective pale to dark grey patina. As a soft material, impact damage is commonly found on lead sculpture in the form of superficial dents and scratches to the surface and as such it is very vulnerable to vandalism.
The conservation and repair of lead sculpture often involves removal of the original armature and core material followed by the insertion of a new stainless steel armature. This may require cutting patches and sections to allow access. These are then lead-burned in place, and the seams carefully worked back and artificially patinated to match the original surface. This process restores the structural integrity of the piece and if performed by experienced conservators, the sculpture will retain the appropriate, aged appearance and will be structurally stable.

ZINC
The manufacture of large-scale sculpture in zinc was only in fashion for a short period, about 1840-1900. The sculptures were cast in sections and assembled using lead soldered joints, which were additionally pinned onto structural elements such as iron straps or frames, or zinc plates, for extra strength. The majority of this monumental sculpture was intended for exterior display and was generally finished to resemble bronze or stone. To achieve the bronze effect the completed sculptures were frequently electroplated in copper. Today, zinc sculptures sited outdoors have usually lost their original surface coatings and copper plating through corrosion, exposing the grey colored zinc. The corrosion causes a very pitted surface in the zinc, accompanied by failure of the lead solder joints which compromises the object's structural stability and leaves it vulnerable to serious fracture and ongoing corrosion. There are new techniques used to repair structural damage and restore the corroded surface to replicate the original 'bronzed' appearance.

CAST IRON
The production of cast-iron sculpture began during the industrial revolution in the nineteenth century, as iron casting skills were developed and new production techniques made iron a cost-effective material for sculpture and ornament.
As iron rusts rapidly if unprotected, a high percentage of iron objects including sculptures were originally painted, either naturalistically or to resemble other materials such as bronze or stone, traditionally using lead-rich oil-based paints.
Cast iron is a brittle material, making it susceptible to impact damage and stresses caused by expansion rusting of construction joints in the object. Cast iron can be repaired using a range of techniques such as pinning, stitching or welding. However great care is required when attempting repairs, especially if heat is involved in a process, such as welding, as localized thermal expansion can induce further cracking and subsequent structural failure. Missing or severely damaged elements can be recast and replaced.
It is important that existing paint is analyzed so that original paint schemes can be identified and reapplied as much iron sculpture has been over painted many times in its life.

SILVER AND SILVER GILT
Unlike gold, silver will tarnish, causing initially a light brown staining which will deepen to dark brown and finally, if left untreated, to a compact dark grey or black surface.
The consequence of this has been that most silver articles have sustained wear to the surface as a result of frequent polishing, and possible physical damage caused by the regular handling that cleaning entails. The surface of silver gilt objects is even more vulnerable to damage as the thin layer of gold is easily worn away. To minimize the risk of further damage, measures to reduce the cleaning and handling of silver are crucial to long term care. Conservation of silver and silver gilt objects usually takes the form of careful cleaning, using a variety of gentle techniques which remove tarnish and old polish residues left by years of cleaning. If the particular display circumstances or condition of the piece demand it, it is recommend that you lacquer the piece, which negates the need for polishing. When applied properly, a lacquer will remain in good condition for over ten years and can therefore contribute greatly to the survival of the object and its surface decoration. Small repairs or the replacement of missing pieces may also be required, and this can be carried out using traditional silversmithing techniques.