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Bolt on Climbing Holds
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What is a Climbing Wall

Bildering And Bilderers
Geoffrey Windthrop Young
Arthur Pinner

First True Climbing Structure
Clark Schurman
Camp Long

Post War Development

1960's Boom
Britians First Climbing Walls

1970's Development

Climbing Wall Manufacturers
Bendcrete Climbing Walls
DR Climbing Walls

University Walls
Brunel University
Spire Rock
University of Washington

The 1980's Wall Development
The invention of the bolt on Hold

First Commercial Climbing Centre
Vertical, In Seattle
Mile End, London

The 1990's Beginning of the Golden Age

21st Century Climbing Walls and the Future

The first bolt on holds for artificial climbing walls were designed or devised by Leonard C. Anderson in the late 1960's.

Many forms of bolt on holds were developed in the early days. In the early 1970's Gordon Bendall, before he founded Bendcrete, experimented with glueing rocks to steel plates with epoxy resin so they could be bolted or screwed to plywood panelled climbing walls.

It wasn't until 1985 that Francois Savigny invented the bolt on hold we know it today, and founded Entreprise Climbing Walls.

Many materials have been used over the years to make bolt on holds from rock, concrete, wood and resins. The most popular and practical in the climbing wall industry was resin as it set very quickly and allowed multiple holds to be cast from one mould. Resins used were polyester, epoxy, polyurethane and acrylic but far the most popular was polyester resin, it was cheap readily available, and it soon became any industry standard.


Bolt On Holds
Wikipedia currently has no defintion for 'Bolt on holds' but defines 'Climbing Holds,' an artificially made hand or foot hold used on climbing walls to aid a clmbers progress. They are described as a shaped grip that is usually attached to a climbing wall so climbers can grab or step on it. On most walls, climbing holds are arranged in paths, called routes, by specially trained route setters. Climbing holds come in a large array of sizes and shapes to provide different levels of challenge to a climber. Climbing holds are either bolted to a wall via hex-head bolts and existing t-nuts or they are screwed on with several small screws.

The Anderson Climbing Holds
The first bolt on holds were designed or devised by Leonard C. Anderson and first used in the climbing wall at Royal Belfast Academical Institution in the late 1960’s.

The lack of flexibility that the climbing walls offered at the time was a recognised problem. Anderson’s solution was metal boxes with a nut at the back. These were cemented or otherwise secured into a brick wall. Anderson devised a matrix for their layout. They were fitted at 2’ vertical intervals and 2’ 6” horizontally. Into the housing were fitted a hardwood (Beech) block that could be recessed, fitted flush with the wall or shaped and fitted to project from the wall.

The symmetrical appearance of the hold placements was aesthetically pleasing and is still used to day though the hold density is much greater. It also solved the age old problem of having projecting holds into a multi use sports facility. Insert holds could be fitted up to an 8’ height so as not to cause a hazard when the hall was used for basketball or five a side.
Bolt on climbing Wall Hold Bolt on climbing Wall Hold
Bolt on climbing Wall Hold
Bolt on Climbing Hold, Climbing Wall

West Common Sports Centre, Scunthorpe (photo R Holmes, BMC)

Cast Resin Holds
These have become the industry standard and is what we know today as a bolt on hold.

Francois Savigny was an industrial engineer and rock climber, founded Entre-Prises in 1985 with help from Petzl Climbing Equipment. The first products to be sold were a selection of modular bolt-on holds made from resinous concrete and these were the first commercially marketed cast resin bolt-on climbing holds. The importance of the bolt on climbing hold cannot be underestimated. As for the first time climbs or routes could be created and changed simply by screwing a resin hold on a wall using a standard engineering bolt and fixing. It created a revolution in the design of climbing walls from the heavy cast concrete structures to the lightweight plywood or fibreglass structures we are familiar with. It is interesting to note that in 1988 the BMC (British Mountaineering Council) published the first of it’s Climbing Wall Manuals, (Full tittle - Development, Design and Management of Climbing Walls - A Technical Information Manual for Architects, Leisure Mangers and Climbers) there is not one mention of cast bolt on holds, but concentrated on setting rocks into brick walls or precast concrete blocks with rocks set in them and large cast reinforced concrete features. It was produced on the cusp of the new age of climbing wall development. It was like Punk Rock wiping the floor of the Progressive Rock, or to put it into context Grunge taking over from Stadium Rock.

Early Bolt On Hold Manufacturers
Metolius claim to have been making holds since 1986. Canyon Holds, another French company were probably the next company to start manufacturing cast resin holds. Rockworks were the first British manufacturer of cast resin holds in 1988 and Nicros in USA, have also been making holds since 1988. Today 100's of manufacturers World wide produce climbing holds.

How are Bolt on Holds Made
The bolt on hold has changed little in the intervening years since it was invented in 1985. There are certainly more of them, more colours and the range of sizes is now vast. First the shape is carved often from a closed cell polyurethane foam. The texture of holds is defined by the grade of foam used, and it is similar to Oasis foam (florists foam), but being closed cell it doesn't absorb water. Once carved the holes for the fixings are made into the foam former. A silicone rubber mould is made around the foam former by setting the hold in a box with removable sides. The rubber is poured over and left to set. With the sides removed the silicone rubber can also be removed. The flexibility of the silicone allows the foam former to be removed. The silicone is excellent at picking out all the faint features of the foam. With the silicone rubber turned upside down it becomes a simple mould. The polyester resin mixture is poured into it an allowed to set. Once set the flexibility of the silicone allows even quite complex shapes to be pulled from it. During the setting process the polyester resin produces a exothermic reaction. This heating of the silicone will eventually cause it to harden and become less flexible.

In the late 1980’s there was no standard fixing design each manufacturer used what they thought practical Entreprise used a M10 bolt fixing whilst Canyon used a M12 fixing and also produced glue on holds. A least one manufacturer used M8 bolts. All holds were produced with an inset flat area to take either a cap head or button head bolt. The flat area was often reinforced by casting into the hold a flat washer. By the early 1990’s the industry had settled on an M10 fixing bolt. Many manufacturers changed to a countersunk fixing as they identified the in-situ washer as a weakness as many holds broke along this. The countersunk fitting allowed the bolt a greater surface area contact, and therefore required less torque in tightening to stop the hold form turning or spinning.

Polyester Resin Holds
Most companies that manufacture bolt or screw on holds, climbing holds, still use a polyester resin mixture the type used by many fibreglass companies.

In the Entreprise (UK) brochure, 2011/2012, about 90% of their range is in Polyester resin. Entreprise USA (March 2011) advertises approximately 350 PU holds of their 1000+ hold range. HRT (Walltopia) appear to have close to a 50/50 split with Polyester holds to polyurethane holds. Nicros use corn/soya oil in their holds they do not say what percentage, and presumably it is a polyurethane resin. Bendcrete claim it is the cost of remoulding its holds as the main reason they have not marketed polyurethane holds.

The resin mixtures are good at taking the form in the silicon moulds and therefore can create detailed textures and with variety of silica based fillers can be very durable and less prone to polishing than with resin alone. The longevity of the holds depends as much on the fillers as the type of resin and pigments used and the environmental conditions it is subjected. As well as, how the hold is treated. Many holds on climbing walls have been known to be still in use after 20 years or more. Heavily used holds in a climbing centre may have lost the texture after only a year and therefore replaced even though the structural integrity of the hold is not compromised. Outside they are also subjected to heat and cold. UV degradation of many general purpose resin may mean the holds only last a few years before they become brittle. The colour also fades very quickly outside when inferior pigments are used, so as the holds age they become more and more brittle until they eventually crack.

Because polyester resin holds are not flexible, they will often crack suddenly if they are being tightened down on a wall that is not completely flat, ask anyone that has route set on curved resin walls. A final problem is the weight of resin climbing holds. As hold sizes have grown and grown, in many cases the resin aggregate composite has become an impractical material to use. Even when the hold is hollow-backed, resin aggregate is still quite a heavy material to be carried up the wall in a bucket. We say Polyester as a generic term to refer to both isothalic, orthothalic polyester and the slightly different vinylester. The reason polyester holds are so popular is because it is cheap, usually less than half the price of Polyurethane resins. So despite all the health and safety hazards encountered in production it remained the industry standard for 25 years.

Primary Health Concerns in Manufacture

Eyes - Can cause severe irritation, redness, tearing, blurred vision.
Skin - Prolonged or repeated contact can cause moderate irritation, defatting, dermatitis.
Inhalation - Excessive inhalation of vapors can cause nasal irritation, dizziness, weakness, fatigue, nausea, headache, possible unconsciousness, and even asphyxiation.
Swallowing - Can cause gastrointestinal irritation, nausea, vomiting, diarrhea. Aspiration of material into the lungs can cause chemical pneumonitis
Chronic: Repeated overexposure may cause central nervous system damage, kidney damage, liver abnormalities, lung damage, cardiac abnormalities, reproductive organ damage, skin sensitization and dermatitis.

However because polyester resins contain about 50% Styrene it is classed as type II carcinogen, because of studies on mice showed a significant increase of lung cancers. The Styrene Information and Research Center (SIRC) reported no link between styrene exposure and an increased incidence of cancer has been found collectively in eight studies of workers in the reinforced plastics and composites industries prior to 1992.

Primary Safety Concerns

Highly flammable and contact with strong alkalies, strong mineral acids, and oxidizing agents. Methyl ethyl ketone peroxide (MEKP) is used as the catalyst to harden the polyester resin. MEKP is an organic peroxide and extremely dangerous solvent. It is a very volatile liquid that quickly fills the air with toxic fumes that can cause permanent damage to the central nervous system. A similar organic peroxide was used as a torpedo and rocket propellant. A simple fact that it provides it’s own oxygen to burn and in doing so releases more oxygen to feed more fuel. In contact with copper it will expand hundreds of times at a rate of 5.2km/s. In a confined space this is effectively and explosion. For further reading see the Russian submarine The Kursk or the 2006 transatlantic aircraft plot

Polyurethane Resin Holds
Currently most commercial hold manufacturers are moving to holds made from polyurethane or polyurethane mixtures. Polyester resin holds though still dominate the market. Polyurethane is not new to climbing as those of us who lived through it will bear witness to. When cast bolt on holds were first invented many climbers were wearing it, but they new it as lycra, elastane or spandex. In manufacturers literature they often refer to them as PU holds. They are sometimes wrongly refered to as urethane holds. Urethane is Ethyl Carbamate and polyurethanes neither contain nor are produced from ethyl carbamate. Polyurethanes, especially those made using aromatic isocyanates, contain chromophores which interact with light causing deterioration, therfore may not be suitable for long term outdoor use.

Polyurethane is a better product for holds because it is lighter, more flexible, and less prone to chipping and breakage than resin or natural materials. More importantly there are less of the health and safety effects associated with polyester resins. Like other resins, polyurethane mixtures can vary, and different mixtures have varying strengths. The manufacturing principle is the same as polyester resin. Measure the liquid isocyanate and resin blend at a specified ratio, mix them together with any fillers until a homogeneous blend is obtained, dispense the reacting liquid into a mold, wait until it cures, then demold the finished hold.

Primary Health Concerns
R36 Irritating to eyes. R37 Irritating to respiratory system. R65 Harmful may cause lung damage if swallowed
Primary Safety Concerns

Future Development - Corn (Maize) and Soya based Resins
In February 2009 – Nicros owner and President Nate Postma announced that, Nicros, is proud to be the first climbing handhold manufacturer to introduce the use of an environmentally-conscious, Corn/Soy-Based resin into its Super-Mix recipe. This resin, made from renewable resources, is now used in the production of all Nicros and PM Climbing Systems training tools and handholds. Postma said, “This new resin is an important step forward in supporting the effort to reduce petroleum consumption.”

These are known as natural oil polyols, also known as NOPs or biopolyols, are derived from vegetable oils by several different techniques, and the primary use for these materials is in the production of polyurethanes. Since 2004 the biggest investor in these has been Ford who have used polyurethane foam derived from soya oil in it's car seats since 2008. We have yet to see any significant change in the marketing of bolt on holds in favour of polyols, but it is certain that major manufacturers of polyurethane will be introducing it into their resins.

Page Acknowledgements and References:
Wikipedia - Polyurethane


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