(Book and Paper 2018) Cocktails and Mixers: Ethanol-Modified Treatments for Iron Gall Ink by Julie Biggs, Lynn Brostoff, Andrew Davis, Claire Dekle, Cyntia Karnes, Yasmeen Khan, Susan Peckham, and Cindy Connelly Ryan
Calcium phytate (phytic acid) and calcium bicarbonate treatments have been successfully used to address iron gall ink corrosion of paper by slowing the mechanisms of deterioration. Water-sensitive inks can be affected by aqueous treatment, a problem that can be mitigated by adding ethanol to the treatment solution. In order to create ethanol-containing iron gall ink treatments, conservators and scientists at the Library of Congress undertook a multi-year study to find optimal ratios or "cocktails" of ethanol with water-based iron gall treatment baths.
The variables selected for comparison in the research were:Cation choice: calcium phytate or magnesium phytate
Calcium phytate is affected by pH - as pH is raised from 4.8, precipitation begins at pH 6. Ethanol creates even more precipitation - does this create deposits on the document? Magnesium phytate is more soluble than calcium - does this allow more room for ethanol to be added to the bath?Concentration of magnesium phytate: standard or half concentration
Half concentration solutions had less precipitate. The standard concentrations used were:
Calcium phytate standard concentration: 2.28g phytic acid (50%w/v) and 0.44g calcium carbonate per litre
Magnesium phytate standard concentration: 2.28g phytic acid (50%w/v) and 0.7g magnesium carbonate per litrepH of magnesium phytate: acidic (5.5-6.0) or alkaline (7.5)Percentage of ethanol in admixture: 50% or 65%
To replicate historical examples, samples were created using a pen plotter with iron gall ink to draw patterns. The ink was made using the same recipe as the previous LOC study, it is not a particularly corrosive ink and this allowed subtle differences to be seen. Although gum arabic may add complexity to the study, the aim was to approximate an historical ink.
The samples were aged for 3 days to induce a uniform state of oxidation. The samples were put through 3 baths of 20 minutes each. Afterwards, they were put through accelerated aging.
Control samples had more brown/yellow discolouration, showing migration of iron gall ink. Bathophenanthroline indicator papers showed iron for all after 28 days, but phytate treated samples were white at 0 days and fairly white at 3. Standard magnesium and calcium 50% ethanol samples were still okay at 14 days.The paper showed no measurable damage (acidic pH) - in other words, the paper itself did not affect the iron gall ink result. Ethanol treatment did not affect iron all that much more than controls.
Observations via optical microscopy: Samples at 28 days showed darkening and warming of the ink tone. Spherical or cubical deposits were noted.Summary of results:
3-bath wash treatments performed poorly compared to 3-step wash-chelate-alkaline bath treatments
Calcium phytate-bicarbonate treatment was broadly comparable to magnesium phytate-bicarbonate treatment
Best result: Magnesium phytate standard concentration, pH 5.8, 50% ethanol
Worst result: Magnesium phytate half concentration, pH 7.5, 65% ethanol
Magnesium phytate at pH 5.8 leaves slightly more deposits than other phytate-bicarbonate variants
Calcium bicarbonate was not so effective as other alkalisation methods but it doesn’t have an effect on the ink color - there are tradeoffs and choices in all these decisions.
Choice of ethanol-modified calcium or magnesium phytate with calcium bicarbonate
Ethanol ratio of 50% is preferable
Magnesium phytate at pH 5.8 does not require pH adjustment with ammonium hydroxide
All ethanol-modified solutions leave some deposits
With preparation, replicable ethanol-modified treatments can be undertaken in conservation labs
Julie Niven, Archives Conservator
Mills Memorial Library, McMaster University, Hamilton, Ontario