Q.  Regarding the restoration of gilded frames..."I usually stabilize loose gesso with watered down PVA glue but is this the best way to stabilize the gesso or is there a better product that I should be using?

Secondly, how do you set about matching the existing patina?

~ Brian, UK

A. I assume you refer to Polyvinyl Acetate (white glue) rather than Polyvinyl Alcohol which may be used by conservators in certain gesso applications during conservation. There is some difference of opinion in the choice of materials for gesso consolidation which can range from delamination of gesso segments to friable or flaking gesso. A weakened PVA emulsion with a wetting agent is a demonstrated method to help consolidate flaking gesso. For re-attaching loose sections of gesso and re-adhering gesso that is delaminating from the wood surface I recommend using a 10% RSG (rabbit skin glue) solution with a drop of ox gall during application to retain the same traditional protein binder that would likely have been originally used on your frames and in the gesso.  

To prepare a 10% solution, soak 1 part dry RSG : 9 Parts Distilled Water and then heat to no more than 120F. If necessary to facilitate the Size under sections of gesso or into crevices, slightly dilute the RSG solution to ease its way but maintain the full 10% glue strength wherever possible.  

If gesso has 'blistered' to where it is no longer securely attached to the wood and there is no entry point to insert the RSG, consider drilling a very small hole in the gesso layer to inject a small amount of glue through the opening and apply gentle pressure to the gessoed surface to help stabilize it. This should be a last resort as one of the main goals during treatment is to maintain the original finish as much as possible; however, if the gesso is blistering and is no longer attached to the substrate it seems an approach that is the least invasive to gaining access to the underlayer of the delaminating gesso.   

To protect the gilded surface before gesso consolidation treatment, apply a solvent-based resin to the area of gilding to be protected which can be reversible such as Soluvar or Acryloid B-72.  Maintain care that the resin remains strictly to the surface area. 

Matching the existing patina of exposed gesso and of a gilded surface represents some of the art of gilding. There is much to consider as this is a complex area. You may wish to research the Gilding Arts Newsletter for previous articles that would provide some element of depth.  

Essentially, there are a variety of toning mediums that are used and the proper medium needs to be chosen for the method of gilding used. Raw umber is a color that is used quite often, sometimes in conjunction with other colors. Toners may come in the form of tinted shellacs, RSG-based washes, casein, asphaltum, Japan paint, and others. The process of rubbing the leaf and applying clear RSG solutions or matt-Soluvar as a topcoat also contribute to toning.      

The topic of gesso treatments and consolidation are discussed in great length in this month's book recommendation Gilded Wood. 

Q. "What is the best way to see if it's real gold or metal leaf?"...and also "What to use on worm holes under old gesso?" ~ Malin, Sweden  

A. Generally, the first indication whether you are looking at metal leaf (also known as Dutch Metal, Composition Gold, Imitation Gold, or Brass or Aluminum Leaf) is to see how far apart the overlaps between the leaves are. Brass or Aluminum leaf is about 5 1/2" wide while most genuine gold leaf measures 3 1/8 - 3 3/8" Wide, depending upon the country of origin (some leaf in Thailand is much smaller). A trained eye can often tell the difference by the tonality and identification of tarnishing which occurs with brass but not 22kt gold leaf or higher. Instrumentation available to conservators can give a specific view of the metal used but generally this isn't necessary for most restoration.  

Concerning worm holes, it's necessary to determine whether the object contains live insects. One way to visually inspect certain objects such as picture frames is to place the object on a large white board overnight and check it the next day to see if there are any tiny black 'droppings'. However, if there is any doubt then one efficient method is to have the object fumigated using a reliable and trusted firm that can do this for you. In Seattle I use Paratex.

Something else to consider, of course, is whether the worm holes present are genuine or fabricated to simulate age. Many times a rue worm hole will have both a point of entry and exit, so look for two holes. But obviously, the can be reproduced as well.

As for restoring gesso that has experienced insect infestation, adding garlic to the new gesso can act as a natural fungicide (while adding an aroma to your studio at the same time!).    

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