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Localized stain reduction using small gel blocks of 3-4% agarose with sodium citrate pH 6.5

Localized stain reduction using small gel blocks of 3-4% agarose with sodium citrate pH 6.5

Localized stain reduction tests of agarose gel blocks on papers that have been uniformly dyed with coffee (left) and chocolate (right). 

As the gel blocks dry out they shrink. Note the larger crescent-shaped cleaned area on the right paper compared to dried gel block. 

Piece of wall removed from the Porter House on the Winterthur Museum grounds. Overall before testing. 

Multiple layers of wallpaper are adhered on top of multiple layers of paint on wooden substrate. 

Final report and conclusions from investigation. 

Initial testing with D4 (decamethylcyclopentasiloxne or cyclomethicone) to determine if it would move any color. The D4 did not appear to have any effect on the color. 

Even with pre-wetting up the test area with D4 the gel block still left a tide line. Excessive amounts of dirt and particulate were coming into the gel block and no effect was noted on the adhesive as the layers did not separate after application of gel with amylase. 

Dried, dirty gel blocks after initial tests. 

Overall summary of areas tested during investigation. 

Ultimately, microemulsions were chosen for additional testing because the concentration of the agarose gel block necessary to introduce the enzyme (amylase) was not high enough to avoid the risk of tide lines even after surface cleaning. 

Test areas for each of the four microemulsions

Testing area after application of microemulsions

No noticeable effect on separation 

Area before testing

Application of micro emulsions

Additional testing area with applied microemulsions

Area immediately adjacent to previous test site was selected for a control comparison with the traditional separation/removal method of steam. 

Overall view of microemulsion test sites and steam (towards right). Notice how the steam test site is already starting to lift. 

Continued application of steam across the two sites and achieved successful separation of top layer using steam

Gel blocks with amylase were test again, this time at the very edge of a layer. 

Application of gel blocks

The gel block was removed before drying out to help prevent tide lines. Here you can see the edge starting to lift. 

Wall fragment overall after testing

As stated in the report summary, it was found that the traditional method of using steam was most successful at separating layers of wallpaper. However, alternative methods such as microemulsions could be easier to apply or introduce into corners or tight spaces where it is not practical to bring a steamer. The emulsions and gel blocks are also safer to use on torn and highly degraded edges where it is challenging to introduce a spatula. 

The evaporation time for D4 deserves further investigation as some of the colors still remained saturated a week after application.