When making a distinction between conservation, restoration and repair, a misconception sometimes arises when “restoration” is understood as a replacement of old or damaged parts with new ones. This indeed is a destructive action with respect to an antique item, as it leads to the loss of primary sources so invaluable for historical research. This conceptual mistake may be due in part to the lack of training in restoration ethics, for example, when attempts are made to restore old pieces of furniture using screws and modern varnishes; or when an old book cover is replaced with a new beautiful binding. This is called “repair” and it is not “restoration”. 

Professional restoration includes both stages of work: 

1) Conservation stage that aims to prevent further deterioration of old materials by stabilizing the condition of the materials from which the original artwork was created.  

2) Reconstruction of missing parts, integrating them with existing ones.  Such reconstruction is made with historical methods used at a given epoch and geographic location.  

Below is an example of the conservation of an icon, 19th century, oil painting on wood.  At this stage of work, the wood board is strengthened on the back side, and the layer of paint is worked out with appropriate conservation methods which ensure that the colours would not continue to crack and crumble.

At the next stage of work, those damaged parts of the painting are going to be reconstructed in a historical technique: i.e. the same materials are used to rebuild the plaster basis, to cover it with an underpainting colour, and finally to paint over the missing piece of the image, being very careful not to touch the old painting that is preserved. 

This is a common practice in restoration work when up to 30% of an object is damaged, but sometimes, depending on the context and value of objects, they can be reconstructed even when only 30% of the original is preserved. However, debates can be often encountered, especially in the North American context, that question the professional ethics of one who does restoration work and claim conservation as the only legitimate action with respect to antique objects.  This is due, in part, to the lack of restoration traditions in general, when compared with the European educational programs and common restoration works performed at the museums and for the private sector, and in part to different definitions of what an antique object is, when for example Canadian auctions sell 70-year-old pieces as antiquarian objects of value, while in Europe such objects are normally sold at street markets or gift shops. 

It is worth mentioning that a restorer of artworks is also a scientist, researcher, historian, and professionally trained artist. 

The historical method is a number of techniques, methodologies, and materials used in each given epoch and culture. Thus, historical reconstruction implies both theoretical knowledge of the history of arts and practical skills of making replicas in all those techniques, so one can create copies or rebuild damaged or missing pieces of old objects in a given style, using appropriate methods, and in a way intended by the creator.  Research is an important part that is done before we can even touch an old object in question. Restorers normally identify, evaluate, and research primary and secondary sources in order to determine the exact technique and style in which an object was created and therefore be able to construct an accurate replica of missing parts. 

In any case, the new additions always differ from the old materials. Such a method is widely used in restoring paintings, sculptures, and objects of decorative arts. "Reconstructing missing parts" is not a synonym for "making the object look nice", as some may interpret. That work would allow scholars, students, and the general audience to see the object in its integrity as it was before. Such work aims to preserve the original and make the item usable again and not merely stored and studied. 

The result of the restoration process, when carried out following historical methods, is always reversible and is carefully documented with before-during-after photos and descriptions for future restoration work and research.