Summary of survey findings

1. What materials have you or your colleagues / institution used for gap-filling wooden objects in the past year? [If any]
"The aim of this question was simply to collect a list of materials that conservators were currently using to fill wood, in order to see the extent of the range, and the popularity of certain materials within it, specifically Klucel G and paper pulp."
·               This was an open question.
"·               The most mentioned adhesive was Paraloid B72 (41% of those who responded to the question), followed by HPC (18%) and epoxy resin (15%)."
"·               The most mentioned bulking agents were microballoons (51%) followed by paper pulp (22%), tissue (21%) and wood (20%). Glass and phenolic microballoons were both mentioned, although sometimes the type was not specified."
"·               B72 was often teamed with microballoons, and HPC with paper pulp / tissue, but also microballoons with HPC and B72 with cellulose-based bulkers."
"·               Also mentioned: wood dust and PVA, fumed silica, plaster, wax, commercial off-the-shelf products, coconut shell powder, cork, cotton fibre, animal glue, paper mache, Flügger, emulsions, Mowilith, and Plastazote. As well as pigments. A wide range of materials. "
·               Also mixtures of bulkers were common e.g. microballoons and paper pulp.
"It appeared from the comments that conservators employed in different areas had different approaches, for example conservators in museums tended to mention synthetic adhesives such as B72, whereas furniture restorers were more inclined to list natural products such as waxes and animal glue. Of course, the choice of material would depend on the role of the fill and the role of the object; furniture tends to be repaired using traditional materials and methods that mimic the original construction, and furniture will often be used again, whereas fills in museum objects are more often small and for aesthetic reasons, and do not necessarily need to be robust enough to withstand frequent handling."


2. Which of the following materials would you consider using to gap fill wooden objects? 
"The aim of this and the next question was to find out whether conservators thought that HPC was a viable adhesive for mixing a filler for wood, and whether paper pulp was a viable bulking agent. It was also interesting to see how many people would rule it out as an option, and what else they would consider – would it be other synthetics, or natural materials such as animal glue? "
"·               Comments indicated that the list was not exhaustive, e.g. I didn’t include Flügger, or hydroxypropylmethylcellulose (Culminal)."
"·               The most mentioned adhesive was acrylic resin (75%), followed by HPC (42%) and wax (42%). Less than half of the respondents therefore considered HPC to be a viable adhesive for forming a filler for wood. However, just over half of the respondents said they would consider at least one of the cellulose ethers listed."
"·               The most ticked bulking agents were glass microballoons (68%), balsa wood (59%) and paper pulp (49%). Only half of the respondents considered paper pulp to be a feasible bulking agent for wood fills."
"·               Two thirds of respondents who said they would consider HPC also said they would consider paper pulp; and two thirds of those who would consider paper pulp would also consider HPC. These are much higher proportions than among all respondents, suggesting that these materials might be considered as compatible for wood fills, especially because they are mentioned together in question 1."
·               Epoxies were said to be used only with a barrier (usually acrylic resin) on the wooden surface.
"·               Of course, this question was not subtle enough to cover the fact that every fill has different requirements. Some respondents said they would consider anything, because nothing should be initially ruled out when planning a treatment. However, no-one ticked all of the options."
None of the options received no ticks at all.
"·               Some people put caveats on their answers e.g. using an acrylic resin barrier, or using only a particular type of wood / brand of adhesive."

Quotes:
"“TIP: Try (within reason) not to rule out materials and limit your choice, chances are there will always be an occasion where you will find an appropriate use for most materials.” "
“My approach to gap filling has always been as basic and simple and reversible as possible.”
“The choice of filler composition does depend greatly on what you are filling; its requirements and condition - there should be no single standard treatment”


3. Which of the following materials would you NOT consider using to gap fill wooden objects?
"·               Linseed oil (73%), plaster (69%) and silicone rubber (67%) were the materials most likely to be disregarded, the latter despite the work by Barclay & Grattan (1987) and Storch (1994)."
"·               Most (over 50%) would also not consider AJK, epoxy, urushi, or cellulose nitrate. Views on epoxy were very variable, although it appears that people would consider it as a component of a fill but not as an adhesive to be directly used onto the wooden surface."
"·               16% would not consider HPC. 10% said they would not consider any of the cellulose ethers listed. The respondents who said they would not consider HPC did not trend towards choosing synthetic or natural alternatives; popular choices for this group were acrylic resin, glass microballoons, and balsa wood, but nearly all of the other options were also ticked."
"It appeared from the comments that conservators employed in different areas had different approaches, for example conservators in museums tended to mention synthetic adhesives such as B72, whereas furniture restorers were more inclined to list natural products such as waxes and animal glue. The reason for different approaches here is not simply where the restorer/conservator worked but rather the nature of the work and the future use of the objects. i.e. furniture being restored can be considered as ""working objects"" therefore the approach needs to be more interventive and often requires materials of greater strength."


Quotes:
“I will consider any material and weigh its merits for the job in hand” 
"“As a general rule of thumb, I would try to avoid materials which would unable future treatments or have drawbacks”"


4. What properties do you consider to be important when deciding on materials for gap filling wooden objects?
·         Most respondents considered retreatability to be an important factor (84%).
·         Low amount of shrinkage on curing was also important (81%).
·         Similar reaction of fill and wooden substrate to relative humidity (RH) was thought important by 75% of respondents.
"·         Respondents were split on whether the fill should have high or low adhesion to the substrate (27% vs 26%), probably because this depends on circumstance."
·         Two thirds considered high flexibility to be important (it is not clear how this corresponds to the high level of interest in B72 in previous questions).
·         People found this question difficult to answer because the responses are so dependent on the circumstance. 

Quotes
"“[I’m looking for a ] material with properties as similar as possible to wood in composition, pH and reaction to relative humidity, but under wood hardness and strength, and with an homogeneous behavior.”"
"“The level of flexibility, adhesion to substrate and compression desired for fill would vary according to wood being filled, i.e. whether or not it's archaeological, and the condition and strength of the wood.”"
"“We look for fillers which will fill the gap, hold the shape but allow the wood to expand and contract without rupture.”"
"“I have found it best to aim for a filler … that has a similar density, but a little less, than the wood around it.”"
“Probably all these factors should be taken into account dependant on what you wish the filler/adhesive to achieve.”