INSTACOLL is an imported acrylic based, water soluble product developed by Kolner a German company that manufactures gilding related items.  INSTACOLL is a synthetic raising preparation that will provide a high gloss shine on indoor and outdoor gilded projects. Originally made for the moulding industry.

It is recommended that patent Gold be used for this sizing.  Application of the size is generally provided by brush. According to the manufacturers direction, INSTACOLL can be diluted with water no more than 15%. A thin watered down layer is applied first. Then once dry a second layer of INSTACOLL in full strength can be applied on top of the original coat.

After INSTACOLL has been applied, the tack time becomes critical in order for the size to accept the Gold. The window of opportunity for applying Gold should be done as soon as the laying of the size has dried and still holds enough tack to accept the Gold. On paper, usually an hour. 

There may be some climate relationship as to humidity in the area the process is being done. If the tack time passes, the Gold will not adhere.  

There is an additive that Kolner does sell that can be applied on top of the INSTACOLL to revitalize the tack. The additive can be applied anytime. However once the additive has been used, the shine will be reduced substantially.

The mirror gloss is obtained when gilding is done on a smooth surface and the INSTACOLL is built up while being applied. There is some shrinkage as this mix is not plaster based !  Cotton can be used to burnish first through a glassine paper, and it is my suggestion that an Agate burnisher be used if gilding directly. 

Use your teachers direction with this product . Also please note the disclaimer that Kolner includes for reselling dealers: 

The guarantee by the manufacturer and the freshness of INSTACOLL will be voided if not sold in the original Kolner container. Kolner only offers a two year shelf life on INSTACOLL, 
INSTACOLL information