Aquazol® 200 (1 kg)

Aquazol® 200 — The adhesive and consolidant you apply in one solvent and remove with another

Aquazol® 200 is a poly(2-ethyl-2-oxazoline): a linear, tertiary, thermoplastic polyamide that is soluble in water. It is not a cellulose ether like Klucel® G, nor an acrylic like Paraloid® B-72, and that is what decides how it is used — it dissolves in water as well as in ethanol, isopropanol or acetone, but not in acetates or hydrocarbons, so it can be applied in one solvent and removed with another. The number in the name is its target molecular weight, 200,000, declared by the manufacturer and never measured; it places the 200 as the compromise grade of the range: it penetrates reasonably and it bonds reasonably.

Aquazol is manufactured by Polymer Chemistry Innovations (Arizona, USA) as a technical polymer for industrial use, and its documentation does not mention Conservation-Restoration (C&R) among the product's uses. The party that declares it for the sector is C.T.S., who is the one that supplies it to us: their safety data sheet states verbatim «identified relevant uses: conservation restoration», and their technical data sheet is written for conservators. What supports its use on artworks is the published C&R literature — the Getty Conservation Institute tested it in 1994, and since then it has been documented by the WAAC newsletter (Western Association for Art Conservation), the Universitat Politècnica de València, the journal Ge-conservación and the Library of Congress. We say it this plainly because it is the information a conservator needs in order to decide, and because anyone can check it.

What is it used for?

There is no single concentration: there is one per job. C.T.S. gives the range of industrial origin —10 to 25 % in water— and the published literature goes considerably lower depending on the case. To improve penetration on non-polar surfaces such as oil paintings, C.T.S. recommends adding around 10 % ethyl alcohol to the aqueous solution: this is an addition of ethanol to the water, not a 10 % solution in ethanol.

• Consolidating matt or powdery paint layers — at 1, 3 and 5 % w/v (weight/volume: grams per 100 ml) in propan-2-ol:water 1:1; at 5 % the finish stays matt (Castro Simarro, 2020).
• Fixing flaking paint on works that do not tolerate water — two Vietnamese portraits with highly soluble zinc sulfates were treated with Aquazol 200 at 2.5 % w/v in propan-2-ol, chosen after ruling out eight other products (Ebert, Singer and Grimaldi, 2012).
• Re-adhering polychromy and fixing layers where moderate adhesive forces are enough — this is the use C.T.S. declares in its technical data sheet.
• Water gilding — removing animal glue residues with water is always a risk for the gilding; Aquazol residues are removed with acetone (C.T.S.).
• Cracked and lifting oil paint — 10-15 % in ethanol:water 90:10, flattening with a heated spatula (Arslanoglu, 2004).
• Pre-coated repair tissue for paper — 10 % w/v in deionised water, reactivated with a tacking iron at about 95 °C for 5 seconds or with ethanol (Library of Congress and NARA, the National Archives and Records Administration, 2019).

Why choose Aquazol® 200?

• It ages by depolymerising, not by cross-linking. In the Getty Conservation Institute test (Wolbers, McGinn and Duerbeck, 1994), after a dose equivalent to some 24 museum years the films were still fully re-soluble and free of gel fraction, because the polymer tends to depolymerise rather than cross-link. The condition travels with the figure: that test measured grades 50 and 500, not the 200.
• Applied in one solvent, removed with another. Water, ethanol, isopropanol, acetone, methanol, methyl ethyl ketone and methylene chloride — but not acetates or hydrocarbons. The literature points to this as one of its strengths (Arslanoglu, 2004) and C.T.S. turns it into protocol in its removal section.
• Clean composition: 99.9 % polymer and less than 0.1 % residual monomer. C.T.S. itself makes the argument: it is used «without having to introduce co-formulants with it, present in all emulsions or dispersions».
• At low humidity it does not turn rigid. Where animal gelatines harden and lose elasticity, Aquazol keeps it (C.T.S.).
• It does not close the door to other adhesives (Arslanoglu, 2004). And the grades can be mixed together or applied in succession (C.T.S.); the literature gives the concrete move: the 200 first, to penetrate, and the 500 behind it, to bond (Arslanoglu, 2004).

Where it must not be used — the limits C.T.S. puts in writing

• Not outdoors, and not where relative humidity can be expected to rise above 85 %. Beyond that it gels and loses adhesive and consolidating capacity. This is an express prohibition from C.T.S. in its technical data sheet, not a recommendation.
• And the published literature is stricter still: the granulate starts to become tacky from 65 % relative humidity and the film from 70 %, with a recommendation not to exceed 65-70 % in uncontrolled environments (Muros, Cotsen Institute, University of California, Los Angeles, 2012). Gelling and becoming tacky are not the same thing, which is why both figures coexist. Margin can be bought with the solvent: film prepared in isopropanol:water 70:30 withstands five percentage points more relative humidity than the pure granulate.
• It is not suitable for structural bonding. It must be avoided where the joint has to bear shear or tensile load from weight. It is a weak adhesive, and the supplier itself places it: weaker than acrylics and vinylics, stronger than Klucel® G. The 200 bonds slightly less than the 500. Its place is where moderate adhesive forces are enough.
• It is not soluble in acetates —ethyl, butyl and amyl acetate— nor in hydrocarbons, whether aliphatic or aromatic.
• Unpigmented or as a transparent glaze, there are better options for retouching: the very source that measured it advises against this (Jacqmin and Soldano, 2020). The intermediate case —a toned but barely covering glaze— has not been tested by anyone.
• And one institutional case that ruled it out: on the sarcophagus of Butehamon (Musei Vaticani, Prestipino et al., 2015) Aquazol 200 at 10 % w/v mobilised the blue colour and left a certain gloss; the study was resolved with three other materials, one of them Klucel® G. We would rather you got that fact from us.

When Aquazol® 200 and when another material

• Klucel® G (500 g) — hydroxypropyl cellulose. It is the direct comparable: C.T.S., which distributes both, places Aquazol as the stronger of the pair. Klucel® G when the finish has to stay very matt or the work has a plant-gum binder that water mobilises; Aquazol® 200 when a little more bond is needed, or the ability to choose the application solvent.
• Paraloid® B-72 (1 kg) — acrylic copolymer. C.T.S. places Aquazol as weaker than acrylic adhesives, and B-72 is one. Paraloid® B-72 when bond strength is needed or working with organic solvents is not a problem; Aquazol® 200 when the work tolerates neither water nor aggressive solvents, or when what you want is for the material to remain removable decades from now — the underlying difference between the two is the ageing mode, not the strength.
• Wheat starch (1 kg) — the traditional standard for paper, and nobody disputes it. Starch when water is not the problem; Aquazol® 200 when it is —running ink, cockling support—, because it can be applied in alcohol and reactivated with heat or with ethanol. No published test pits the two against each other with figures.

Presentation and storage

• Presentation: 1 kg pack (C.T.S. supplies this material in 1 kg and 5 kg)
• Solid granulate, light yellow in colour, which is the manufacturer's specification
• Keep the container tightly closed, in a cool, dry, ventilated place, between 5 and 35 °C
• Protect it from moisture. Once opened, close it carefully and store the container upright
• Keep it away from strong oxidisers and from strongly acidic or alkaline materials, and out of contact with food
• Neither the manufacturer nor the distributor declares an expiry date. What they do declare is that the product is chemically stable under normal handling and storage conditions

Aquazol® is a registered trademark of Polymer Chemistry Innovations, Inc. (Tucson, Arizona, USA). We supply it in the original 1 kg container through C.T.S. España, reference 01162801.

Frequently asked questions

Any questions? Write to us on WhatsApp, visit innovart.art or email us at info@innovart.art and we will advise you.