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How to tell if a hold is wet

It looks dry, lets climb!

Please read my article on the formation and fragility of Fontainebleau sandstone to understand quite why it is so important not to climb on wet rock here in Bleau. (read this) It is not just to keep you safe, but to preserve our playground. The thing is, that sandstone is porous, and it’s difficult to know just how long to leave the rock to dry before it becomes less fragile again. We say that 2 days no rain is a good guide, but this so variable. Some seepage lines take weeks of dry weather to become climbable.

2 days? Really? But I’m only here for the weekend? Unfortunately you do not have the right to damage the rock just because your vacation is too short, but the reality is that there are areas that dry more quickly.

- Exposed, ridge-top rock will tend to dry more quickly, especially as it is often less densely vegetated, and South facing, sunny aspect boulders will be the first of those to dry. Unfortunately these areas are often sandier, and cleaning your feet becomes extra extra important. Sand stuck on sticky wet rubber acts like sandpaper on delicate rock.

- Harder quartzier rock will dry faster as it is less porous, and holds less water. Fortunately this type of rock also often finds itself on the exposed ridgelines.

- Wind and low humidity make an enormous difference, and dry breezes will definitely dry rock more quickly, however, this is superficial dryness, and it is important to make sure that the underlying rock is dry too.

Ultimately it doesn’t matter where you go, there will still be wet holds within 2 days of rain. So, how do you know if a hold is too wet to use?

  • Colour
  • Wet rock is often a darker colour than dry rock. Sometimes there seems no reason for that dark spot to be wet, but the seepage lines within the block are not evident from the outside, and who knows where the moisture will arrive at the surface?

  • Feel
  • Wet rock doesn’t always make your hands wet when you touch it. Often the moisture is under the thin crust, but if you have a light dusting of chalk on your hands, and touching the hold immediately tuns it dark, do not use that hold. Wet rock often feels colder too, or claggy. That high moisture feeling that makes your hands feel a little sticky is a sure sign there is too much moisture to climb.

  • Sound
  • This seems like an odd one, but if you gently tap a hold the tone could tell you if there is moisture within the rock. Waterlogged sandstone often has a slightly lower pitch than dry sandstone.

  • Location
  • Sometimes the shape of the boulder will tip you off to possible damp holds. In a groove or run-off, or below a hanging groove, will often concentrate moisture, as will cracks and obvious seepage lines. If the rest of the climb is dry, but your one hold in the groove is wet, that means that you cannot complete that climb. I’m sorry, go choose something else to try.

    Drying rock

    Sometimes you will see people trying to artificially dry the rock, either with chalk brushed into the wet area, in an attempt to draw out the moisture, or with big Makita fans. Neither of these are good solutions. Firstly, brushing chalk into wet holds is purposefully abrading wet rock when it is at its most delicate. Secondly, Makita fans are a nuisance to wildlife in the form of mechanical noise at a pitch that may not bother us, but to creatures that operate on different frequencies it could be seriously disorientating. Both of these drying methods also address only the superficial wetness of the rock, and leave the inside waterlogged and delicate.

    Yes, holds break

    Holds do break, and not every broken hold is a result of inconsiderate climbers, but if we can encourage awareness, less damage will ultimately be done. However, what happens when you do break a hold? Should you get some sika and stick it back on the same way you do with limestone? Here in Font the general consensus is NO! Once a hold has broken it stays broken. The route may change in grade, or become unclimbable, but that’s just the way it is. Everything that artificially alters the nature of the rock, such as chipping or gluing is definitely not welcomed in the forest. Occasionally, in the past, weak cracks on classics have been reinforced, so you may see old sika in places, but please do not take it upon yourself to do this. It is not considered good practice.

    The best way to look after our forest is to learn about it and help other people to be aware of their impact. Here is a full video of ways to spot a damp hold on sandstone. Feel free to show it, share it, and discuss it wherever, and with whomever you like.

    Signs of wet sandstone

    Thank you for your respect.


    Helen’s hidden , November 10, 2023

    Sympa cet article qui essaie de décrire ce que signifie le grès humide au lieu de juste critiquer les grimpeurs qui cassent des prises . Je rejoins entièrement ton analyse sur le fait que le grès d'apparence sec reste fragile quand l'intérieur du caillou est humide. C'est ce qui se passe généralement sur l'ensemble de la période automne hiver et début de printemps. La seule période vraiment sèche serait l'été mais malheureusement les températures ne sont pas favorables à la performance. Pour ma part ,c'est un problème insolvable car la plupart des grimpeurs (locaux inclus) grimpent durant cette période... . La seule chose possible c'est de proscrire la grimpe quand le caillou est humide au toucher, pour le reste des conditions c'est compliqué.
    Bonne grimpe à toi 😉

    Helen Dudley

    Mum of Sebastian, 11, and Theo 8. Living in Arbonne-la-Forêt.

    After making transitions from trad, to sport, to motherhood, Helen now lives in the Fontainebleau area dedicating as much time as possible to bouldering and playing in the forest with her two boys.