4. What properties do you consider to be important when deciding on materials for gap filling wooden objects?,,
Table gives data in descending order,,96 responses
,,
,Response,Response
,Percent,Count
Retreatability,84.4%,81
Low amount of shrinkage on curing,81.3%,78
Ability to colour with pigment,78.1%,75
Ability to be reshaped after curing (e.g. by sanding),76.0%,73
Ability to paint after curing,76.0%,73
Material is similar to wood in terms of reaction to relative humidity,75.0%,72
High flexibility,65.6%,63
Texture,61.5%,59
No colour change on ageing,49.0%,47
Low level of hardness (compressibility),45.8%,44
High adhesion to substrate on curing,27.1%,26
Low adhesion to substrate on curing,26.0%,25
High level of hardness (compressibility),16.7%,16
High tack when wet,13.5%,13
Low tack when wet,12.5%,12
Low flexibility,10.4%,10
Material is dissimilar to wood in terms of reaction to relative humidity,9.4%,9
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"36 respondents also left comments (open text, optional)",,
"physical properties such as flexibility, adhesion and hardness need to be adapted to the specific requirements of the fill",,
"I understand this is a very general survey, but it would really depend on the object. It would also depend if the fill is providing internal (unseen or mask-able) support or will be in a highly visible area. It depends on what sort of loads it will take on and the grain and structure of the wood to predict its behaviour in high/low/changing humidity. I have ticked 'epoxy resin' above. Although the chances I will use it with wood is slim, I would still consider it depending on the circumstances. For example, in the case a wooden structure needs axial support with compression from above, I'd consider making a resin ""block"" to insert into the cavity. But I wouldn't use it to adhere wood directly as the epoxy won't respond sympathetically.",,
Many of these answers are contradictoray because different properties are required for different objects.,,
"It is difficult to pinpoint specific properties as depending on the situation, different properties will be desired. I wouldn't rule anything out - you never know what tricky circumstances you will be faced with and will need to find materials to suit.",,
fill material is less strong than the wooden substrate so the fill will crack as opposed to the original wood,,
"These concepts are very difficult to evaluate and generalise on; and several are not mutually compatible. The flexibility question depends on the needs of the object - is movement of the wood likely to occur and therfore flexibility is needed? or not ? Most fills exhibit no reaction to RH and therefore the first two questions are not particularly relevent compared to the flexibility and compressibility factors, where it is the wood itself that is moving. The requirements will also differ according to whether the wood has been treated, eg consolidated with a resin ; or archaeological wet wood being treated with PEG wax",,
"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.",,
"Low toxicity Ease of application. E.g. Stickiness, how runny it is, etc Time - does it have to be done quickly ( does the mix remain usable for a while) or is there a long time on which it can be applied and moulded into shape. Aeging of the material, not necessarily on the colour front, but rather if it becomes brittle or irreversible.",,
"Difficult to say what sort of tack and adhesion are important since it will depend on the requirements of each particular object. Also, reshaping and ability to colour with pigment is important but depending on what type of fill is involved, it may not be necessary.",,
Materials which do not react with Polyethylene Glycol with which archaeological wood is treated. Materials which do not add weight or bulk.,,
"The first priority is matching the characteristics of the filler to the needs of the wooden object - making sure it provides enough support, is removable without damaging the object, does not age inappropriately, cannot be mistaken for the original material in future analysis.",,
"The criteria based on which a choice for a filler is made depend entirely on the situation, and all of the properties listed above can be desirable at times. The ones marked are just those that are most often required or considered. In general, the ""ability to be reshaped after curing"" (safely) and the ""ability to paint after curing"" are always important. ""Retreatability"" (reversibility), for instance, can be ""engineered"" through the introduction of barrier layers. Color fastness is usually less important as most fills will be inpainted. Adhesion is only important when the fill is structural, or very shallow. I would also add ""viscosity"" (when uncured) to the list - too viscous means you can not inject, for instance, while low viscocity means a fill will not hold its ""shape"" while curing. In my experience it rarely happens that the criteria usually listed as most important (similarity to wood in reacting to RH; high flexibility) are indeed important. In those situations where the response to changing climates is most extreme (panels) the cracks or splits are nowadays simply accepted as inherent vice and left untreated. In the rare case that a decision is made to fill such a crack (for either esthetic or structural reasons) it is almost always best to use wood rather than a ""plastic"" material.",,
"This a little difficult to answer without understanding the substrate, the condition and use of the wood as well as the purpose of the fill material.",,
"I would recommend that, compared to consolidation materials, the gap filling material (with mostly aethetic and non-structural purposes) has not only to be retreatabel but also to be removable without damage to the object.",,
reversibility and obviously different on close inspection,,
"Again, I might as well check all of these boxes because everyone of the options might apply in any given situation. I would need to know more about the object, its context and it's proposed use before I make a choice.",,
"The adhesion, hardness and flexibility required all depends on the purpose of the filling and the type of object. According to the level of support required. If it is only cosmetic or has a role in consolidation.",,
"We look for fillers which will fill the gap, hold the shape but allow the wood to expand and contract without rupture.",,
"Desirable adhesion, hardness and tack vary with the situation",,
Ability to mimic surface texture,,
I have not ticked hardness and flexibility or adhesion to the subject on curing as I feel these will change their importance based on the nature of the substrate and the fill. Working on a balsa like substrate would require a different approach to working on a hard ebony like substrate.,,
Levels of flexibility and adhesion depend on the nature of the object and the mend.,,
Flow when when wet for gap filling large holes and channels created by wood boring pests,,
flexibilty and hardness depend on use - is the area likely to be touched or is there much stress? also the adhesion depends on the area to be filled,,
The answers may seem contradictory but the decisions are object specific and variables such as how much structural support is required of the gap fill have to be considered.,,
"As I normally use actual wood slivers, pieces, veneers, the above boxes don't seem applicable. With bees wax see the ticked boxes.",,
All dependent on the type of fill e.g. whether it is structural or aesthetic.,,
"I have found it best to aim for a filler, small gaps, 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.,,
Can't answer this in a tick list - too complex. It depends on current condition and past treatments. Also why the object is being treated.,,
"All of these questions are relevent, it is an intrinsic knowledge of the object itself and the reason why a gap fill is needed that ultimately dictate what choice of fill is used.",,
"Again, depends on the situation.",,
"reversibility, stability, similar materials and technics already used and with proofed results.",,
Desired properties can vary with different objects,,
"I am sorry I cannot choose between any of the choices above, because the properties needed depend entirely on too many factors. Eg. on the type of wood, location of the join, strength needed, condition of the wood, end purpose for the artifact, aesthetic restrictions, surface treatments, reversibility needs, etc. All of the above might be considered important properties depending on the circumstances, and none are more important than others necessarily.",,