September 2000 Volume 21 Number 3

Technical Exchange

A Trick for Reducing Solvent Exposure During Inpainting

Anyone who uses B-72 in xylene for inpainting is probably familiar with the frustration of balancing the convenience of an open container of resin with the desire for the minimum exposure to solvent. Until recently, I just juggled lids and brushes and generally ended up with neither convenience nor low solvent exposure - not to mention a pigment-tainted pot of overly thick B-72.

Well, no more! I've found disposable polyethylene transfer pipets to be ideal for delivering the resin. Fill the pipet, deliver a drop of resin anywhere on the palette, and set the pipet aside until more is needed. The resin doesn't spill from a pipet on its side (even when it has rolled off my cart). Solvent evaporation is reduced and the resin solvent mixture stays consistent. The B-72 jar stays uncontaminated by pigments and is only opened to refill the pipet. I've found it cuts down significantly on the amount of solvent exposure during inpainting and also waste and spills. If nothing else, it greatly reduces the number of lidless glass jars with dried brown resinous gunk rolling about in the dark recesses of my tabouret.

My source for the pipets is The Lab Mart (www.labmartexpress.com) 1-800-684-1234, a good resource for inexpensive labware. They come in a box of 500 for $19.95 (#G373572 - graduated 1ml large bulb polyethylene transfer pipets). The same pipet can be used for several days.

Monserrat LeMense

Two Aquazol "Gesso" Recipes

Several people have been singing the praises of Aquazol-based fill materials. An Aquazol "gesso" can be used cold and, very important from the reversibility standpoint, the gesso is soluble in ethanol as well as water.

Hugh Glover offers the following recipe, originally used in the treatment of a gilded baroque frame:

28g of Aquazol 200 (15% in water)
3g glass bubbles (3M Scotchlite)
2g Kaolin
0.6g Cabosil
0.8g Alpha Cellulose (Sigma Chemicals)

It is quick and easy to use for "infilling" losses on gessoed frames. Overfill the loss, then burnish with an agate burnisher to achieve the desired level (preferably a burnisher that is no longer good enough for gilding because this will ruin it.) There is no sanding needed, and no dust.

Mary McGinn offers this simpler recipe that she has used for fills on paintings. It is nice and smooth with excellent working properties.

Mix Paris Whiting with 10% Aquazol 200 in water to a gesso like consistency. Add a small amount of Ethanol. Brush out on a glass plate to check for cracking. Keep in a closed jar and use as you would a traditional gesso.

Do It Yourself Tools

Can't find just the right tool for, say, carving wax fills? Old upholstery springs may be the ticket. They are made of a high grade sprung steel. If you can lay your hands on some of these coil springs, they can be made into excellent tools. Cut the steel to a 2" length. Imbed the steel in a wooden handle with epoxy. Grind the tip to your desired shape. Voila!

Hugh Glover

While working on several reverse painting on glass projects, I found a shaped piece of Teflon to be very useful in pressing paint chips back into contact with the glass. Shaped like a microspatula that has been rounded into a slight "s" shape, the tool's curved tips and rounded edges work well to press flakes back into contact with the glass. If the Teflon is kept clean, the paint chips stick to the glass and not the tool. Sandy has been using B-72 as a consolidant, (diluted 8-10%) with a very small addition of ethanol for wicking and plasticizing.

Sandy Webber

Fast Methyl Cellulose

To make up methyl cellulose quickly, one can exploit the molecule's characteristic of swelling in cold water but not in hot. Add the methyl cellulose to hot water and shake; it will disperse very evenly. Then as the water cools, it will swell and thicken; you can even put it in the fridge if you are really in a hurry. You can have a smooth batch in about an hour. You would have to be careful, of course, if your solution contained heat sensitive components.

Carolyn Tallent

Request for Information

We're soliciting opinions of and experiences with HVLP (high volume low pressure) spray systems for inclusion in a future technical exchange column.

Also

A survey of suppliers is being considered for a future technical exchange column. If you have a favorite source or supplier of conservation related materials, cautionary tales, or pet peeves, we'd like to hear about it.

And in case you ever wondered...

Bar codes were introduced in supermarkets in 1973 and have been expanded to include virtually all products bought and sold. Under international agreements implemented by the European Article Numbering Assn., bar codes are normally a group of 13 digits; each digit is represented by two black and two white lines, and the digit is printed below its symbol. Longer lines at the beginning, middle and end of the bar codes simply identify the beginning, middle and end of the code for laser scanners. Generally, the first two numbers are assigned to a country and the next five identify a specific company. The company then assigns the next five digits to its products, so that each is uniquely identified. The 13th digit is a check digit. Its purpose is to ensure that the code is composed correctly. Like the Hebrew language, the bar code is read from right to left. Bar codes contain no price information. Instead, the host computer in, say, a supermarket, assigns a price to each bar code.