Tutor XG rope test – Thanks to Spanset

I have spent some time at Spanset in Middlewich over the last couple of months, doing my IRATA L1 and a few other bits. Some of you will perhaps know that Spanset have been particularly friendly to cavers, donating large amounts of new rope to expedition groups and competition winners on places like UKCaving forum. On my last visit to Middlewich last week, I was offered some rope to play with and provide feedback on. Although this is not a new type of rope, it is something that is only recently been taken on by Spanset and as far as I’m aware, there are no cavers out there using this stuff just yet. I’ve been kindly given 100m of this rope to test and report back on. If anyone wants to borrow a bit for a day or 2, just ask.

The first thing that some of you will notice is that this looks exactly the same as the Mammut Pro Static that has been available for some time. You might be tempted to click away now as that rope was truly terrible once it had stiffened up, but this is not the same stuff. From my understanding, Teufelberger took over the production of Mammut ropes some time back and now produce similar looking, but different spec ropes. Only time will tell if this doppelganger remains supple.

So, the details are as follows.

Teufelberger Tutor XG 10.0mm
Semi-static EN1891 Type A

Polyamide construction divided into 41% sheath and 59% core.
Stretch in normal use <5%
Shrinkage <6%
61g per meter

Apparently this is designed with teaching in mind (hence Tutor) and as a general rope access rope. Off the reel it feels supple and as you’d expect a new rope. The instructions provided did not give specific advice on whether it needed a pre-soak before its first use, so I did so anyway. Soaking for 24 hours, with 2 changes of water, before air drying and cutting. The 100m drum was reduced to a 44m, 33m and 19m rope, showing some shrinkage straight off the reel (as expected). In use, the ropes are marked up as a 40m, 30m and 18m. This is my most frequently used range and should permit me to get lots of use out of this stuff.

The rope was prepared and logged onto my system on the 1st of September. I’ll be keeping a track of how much use it has and reporting back when I have something interesting to say. I’ll probably start with an initial use post as soon as I can and follow it up with something longer term.

Mineral ID

It is sometimes really hard to relate the minerals I see underground to the professional sample pictures on places like Wiki and Google. All I wanted was to be sure that what I saw was a certain thing. Well, I’ve started a Flickr album showing actual minerals in actual mines in the hope that I can make it easier for everyone else to identify what you’re looking at. There are loads of omissions still, but it is a start!

Sphalerite (Gerionydd) (2)
LCMLA Mineral ID album.
A collection of various minerals that you are likely to encounter in LCMLA caves and mines around the UK. It is hoped that these real sample pictures will aid you in identifying what you are looking at underground. All specimens were collected for education purposes from waste hillocks or loosely on the floor and no mineral chipping occurred!

New Petzl Stop

Rumers have been circulating for a while now about a redesigned Petzl Stop being in development and test. The first pictures have now emerged following an expo in China. Thanks to Qi Woo for posting these on the Rope Test Lab Facebook Group. I have made a few limited observations based on these few images.

From this pre-sale version, we can see the device remains an assisted braking descender but is now marked as certified to EN 15151-2 (2012), which is the “Breaking Device” standard and indicates this can be used as an assisted belay device, which the previous version was not certified to. This would be a major draw for instructed caving where there is a shift away from ‘historical’ use of the current Stop and towards devices with full certification for each job we ask them to do while at work. It’ll be interesting to see this new Stop go head to head with the RIG2 device which is being picked up by more and more cave leaders.
The new Stop is compatible with 8.5mm to 11mm ropes, which just about covers the full range of diameters cavers are likely to need, although not quite down to the 8mm stuff which is becoming more popular with sport cavers. Interestingly, the new Croll S is compatible with 8-11mm rope.
The assisted braking / control handle has changed from a push-in to a pull-down style operation, much like the Petzl RIG or Kong Indy Evo, something that will be welcomed by some, but disliked by others. I am happy about this, as I’m someone who has started to develop hand pain from the current squeeze operated handle after longer trips or many lowered clients.
The device no longer seems to have user replaceable bobbins, as evidenced by the lack of hex head nuts and bolts on the frame. It does seem that both bobbins are made from the same metal, making me think this is a full stainless steel bobbin device, which should give much longer lifespan over the alloy bobbin version. We should also see an end to grey ropes in the kit store now there is no alloy to wear and coat the rope.
We’ll need to wait and see what that little hole is for in the handle. Remote braking release perhaps or just a pre-production moulding feature?

I have not seen a release date for the UK market yet and I look forward to getting my hands on the user instructions when they are issued. What will be very interesting to see is specifically how Petzl supports the use of this device for lifelining (and rescue hauling) as it might be used in instructed caving. Could this be the Stop we’ve always wanted, or will the professional caving market continue to migrate to the excellent RIG2 device, with its multi-function EN standard compliance?

In addition to the Stop pictures, we can see a completely redesigned Freino krab, with its braking spur repositioned to the opposite end of the karabiner when compared to the previous version. Eagle eyed readers will spot that this krab is attached to a red device in the photo below. We are also looking at a new version of the Petzl Simple. This does still have hex head bolts so may retain its user-replicable bobbins. They bobbins even seem to be symmetrical, making them reversible too.
I’m sure we’ll see more in the coming weeks.

I’ll get my hands on one of these new Stops as soon as they become available. Until then, if you need to talk about lifelining or abseil devices appropriate to your underground operation, feel free to get in touch. For technical advice to the outdoor industry or LCMLA courses, see www.undergroundspecialist.co.uk

Holmebank Chert Mine

Holmebank Chert Mine
Fan Entrance lock installation 9th January 2018

Today I was up at Holmebank Chert Mine near Bakewell on behalf of the Derbyshire Caving Association and the Peak Instructed Caving Affiliation. One of the access points to the mine required a new locking mechanism which allowed explorers to access the locking bolt from inside and out.

Using some high strength steel components bought by the DCA, I fabricated up a simple rotating hatch, allowing a person to reach through and access the sliding bolt on the inside of the gate. The hatch is locked with a combination padlock and cavers can obtain the code from the usual source. Currently it is set to the same combination as the other lock on the top entrance.

Many thanks to Ewan Cameron from Evolution Outdoors for the company and assistance installing the hatch today and of course to Joe at the architects firm for his continued support of access to the mine for outdoor centres and instructor training.

Testing the strength of heavy duty caving belts

A Method of Testing the Strength of Heavy Duty Caving Belts

The aim of this little test was to establish a method to test the strength of heavy duty caving belts that did not rely on having access to a load cell. I hoped to produce a simple system that needed very little equipment and that would deliver a test load to a belt that exceeded the minimum strength requirement for its use.

What strength does a belt need to be?

Well, this one is a potential can of worms…. Let’s be clear, the manufacturers do not condone the use of their heavy duty belts for taking any load at all. There is a historical use in cave and mine exploration that involves using the belt for the purpose of slip prevention and security on steep ground. If you were intending to use it for this purpose, you’d need to be sure that the belt was strong enough for that, something that the manufacturers will not say.
We take the figure for a heavy person with kit that is used for some load ratings on PPE equipment: 120kg.
If a caver has a short lanyard which they climb above, ignoring all stretch or slack in a system, we will assume a possible fall of 1 metre onto the belt. The person will then be travelling 9.81 m/s (acceleration due to gravity).

velocity = √ (distance x gravity x 2)

v = √ (1 x 9.81 x 2)
v = 4.43 m/s

Kinetic energy = (v²m)/2

Ke =  (4.43² x 120)/2
Ke = 117.72 J

Impact force = Kinetic energy / Impact distance

iF = 117.72 / 0.1 (arbitrary minimum for complete stop)
iF = 1177.2 N

Impact Force = 1.177 kN

Confirmation:

Force = Mass x Acceleration

F = 120 x 9.81
F = 1177.2 N / 1.177kN

So a 1m drop of a 120kg caver onto a belt, not taking into account any stretch or bounce, produces a force of nearly 1.2kN.

Apply to this any safety factor you wish. Worse case? Twice the force falling onto half the strength of kit due to wear and age: 2 x 1.2kN = 2.4kN force will need to be held for a worst case fall and we halve the strength for old, worn or wet kit so 2 x 2.4kN = 4.8kN.

So as long as we can apply a test force of 4.8kN or more to the belt, we can be assured that the item can hold the greatest possible force we can apply to it even if not in new condition. The only remaining factor of concern is that would applying this force in test render the belt unsafe to use again, in essence, are these tests destructive? Only 1 way find out…..

You could easily argue that this figure is seriously overkill for a belt so you should undertake your own discussion as to the correct safety factor to apply and then make sure you test to that, e.g. 2.4kN using 2 or 3 people on the 3:1 MA system.

Testing

Using 1 very large Corsican Pine and a good sized Birch tree, we set up a pull testing rig with a simple 3:1 theoretical configuration. I used a Rock Exotica load cell to get live feedback on the testing here but if you copy the method, you would not need to use one.

For the estimation of test force we regarded each person capable of pulling 50kg (see Gethin Thomas’ work on tyroleans). Through a theoretical 3:1 MA system that would be 150kg per person. With 5 undertaking the pull reaching 750kg and 6 equalling 900kg or approximately 7.5kn and 9kN respectively.

Kit used (minus load cell): Petzl rescue pulley, Petzl Basic jammer, Petzl Partner pulley, Lyon wire sling for tree, assorted karabiners, 20m rope.

Due to the force expected to be placed on the rope, I did not anticipate that I would be able to untie the end knot (fig 8 loop). This was accurate and the knot had to be cut from the rope end. Bare this in mind with your own rope!

We also used a Petzl Rollclip to redirect the angle of pull to make it easier to stand on the tarmac of the road alongside the trees.

Initially we had 5 people pulling the first test on a Lyon roller-buckle belt (brand new).
This produced a force of 5.9kN with no damage or slippage. This is lower than expected but there was a lot of tightening in the knot and stretch in the rope coupled with a general timidness of the pulling team.

The remaining tests used 6 people to pull. This one was conducted on my 10 year old Caving Supplies square buckle belt (already retired). This belt has nicks, fluff and rust  and comfortably took a force of 7.74kN showing no damage or slippage. Next came my current AV belt, with it’s central maillon removed and directly attached to the pull line. This belt held 7.7kN without failure or slippage.Finally, the pulling team seemed at their most confident that nothing was going to break and send shards of metal and wood at them so they really gave the last belt some pain. This Warmbac square buckle belt was subjected to 8.64kN with no damage or slippage noted at the time.It is not surprising that the force exerted by the pulling team was less than the theoretical 3:1 system implied. In practice with the loss of friction due to bearings and turns in the rope a 2.5:1 is a more real world figure and so our 5 x 50kg pulling average adults could be expected to make 500kg/5kN using this system. Add a 6th person if the ground is poor or your team are small!

Conclusions

Using a system like the one shown here, with 5 people pulling at average strengths, you can apply a force greater than 4.8kN to your test belt.

Once the test is complete you should thoroughly examine the belt to see if any damage or slippage has occurred. Any that do show signs of damage should be retired. Any slippage may be down to the buckle tightening down so consider testing again. If a belt has taken the test load and shows no damage or deformity then you can be comfortably sure that the belt will be fit for its intended use.

Final inspection of belts:
Lyon roller buckle                                5.9kN            No damage, continuing to use.
Caving Supplies square buckle           7.74kN          No damage, already retired.
AV maillon closed harness buckle       7.7kN            No damage, continuing to use.
Warmbac square buckle                      8.64kN          No damage, slight curvature to webbing now when hung vertically which indicates over stretching or broken fibres down one side. Retired from service.

As a side note, I maintain that the Caving Supplies belts are the tanks of the heavy duty caving belt world and, if kept very clean, will ultimately outperform every other type or brand available. I think this test shows that well as the CS belt had at least 5 more years of abuse over the other belts. I will dispose of the Warmbac belt just in case but don’t tend to use these anyway, but that’s another blog post!

Removing Sleeve Anchors (SPITS etc…)

I guess this post is a bit of a continuation from the blog post I did about pull testing SPIT type anchors in 2015. Sorry it has taken me so long to get round to doing this!
The original post can be seen here: http://www.peakinstruction.com/blog/pulling-spit-anchors-back-garden-test/.

One of the points of that testing was to ascertain if the sleeve anchors could be removed from the rock in a cave or mine to either de-clutter the wall or allow a resin anchor to be placed in the same location. This is important from a conservation point of view, these sleeve anchors are a bolt rash on the walls of our caves and once stripped of threads, are there forever…. or so I thought.

Jump ahead to now. Simon Wilson has developed the IC Resin Anchor in the Dales and his website has expanded to become a good resource of information relating to the installation and removal of anchors. Most relevant here is the method that he uses to remove old sleeve anchors, one which I am shamelessly copying here in an effort to spread the knowledge and encourage the tidying up of pitch heads. Simon’s site is here: http://www.resinanchor.co.uk/5.html.

I started with the original block of Stoney Dale limestone used for the original testing in 2015.


 

 

 

 

 

Method used:

  1. If required, dress the rock near your anchor sleeve with a chisel to create a flat area for drilling.
  2. Drill a 6 or 7mm hole immediately next to the anchor sleeve.
  3. Drill a second hole parallel to and as close to the first as possible.
  4. Bore out into a slot using an old drill bit and some wiggling.
  5. Tap the anchor sleeve into the slot using a cold chisel or old screwdriver.
  6. Remove the anchor from the hole. This may well need some jiggling about or a bit of extra chiselling. If possible, screw a bolt into the sleeve to aid extraction.
  7. Fill hole with resin or drill out for the installation of a new resin anchor.

Shown with a SPIT 12mm self drilling anchor:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SPIT 12mm self drilling anchor that had sheared off in a previous test:


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Another SPIT 12mm self drilling anchor that had sheared off in a previous test:


 

 

 

 

 

 

 

 

 

 

 

This removal method works well once you’ve had a little practice and was far less destructive or time consuming than pulling the anchors out with the HAT-28. I also used the same method successfully to remove 10mm lipped sleeve anchors as well (HKD / drop-ins etc…) although have no photos.
As I was drilling so close to the sleeves, occasionally hitting them, this was very hard on drill bits. I melted the head off my cheap 7mm half way through and swapped to the 6mm bit. I’ve just ordered some quad tipped bits from Hilti in the hope that they are tougher. I’ve only ever destroyed one of them in the tough welsh rhyolite of Parc mine.

The remaining triangular hole can then be cleaned out and filled in using an expired resin cartridge with some limestone dust thrown on. It won’t disappear 100% but will be a huge improvement over the old rusty sleeve.
If you plan on re-using the hole for a new anchor, try to position your slot to the intended orientation of the head of a ‘P’ style resin anchor. Once the anchor is placed, make sure the whole hole is filled with resin leaving no voids. You can’t use the SPIT resin vials for this job as they have a set quantity of contents, you will need to have a resin cartridge gun to fill the irregular hole properly.

I hope to begin removing some of the decades of old sleeve anchors in sites now resin bolted and potentially earn some karma points back for anchors of this type that I myself have placed in the past prior to my ‘enlightenment’.

Thanks for reading.

Coiling Caving Ladders

Caving ladders are an integral part of the LCMLA Level 2 award. Being practiced with a ladder not only saves time but lots of faff. It can be hard to pack loosely coiled ladders into tackle bags, meaning they get dragged and thrown about the cave, something that no kit really deserves. Practice coiling your ladders and look well polished on your assessment and in front of your clients.

Struggling with ladder coiling? Collar me for a face to face demo or contact me.

LCMLA Level 2 – Dec 2015

The North Wales panel of the Local Cave & Mine Leader Award scheme has just run a block of courses based out of Oaklands OEC near Llanwrst. I am a member of the N Wales panel and I will be working alongside other T/A’s as I move towards completing my assessor apprenticeship. The centre was host to 2 full LCMLA Level 1 Mine training courses and a full Level 2. There were also a number of people on mine to cave transfers and 1 person on a 3rd day of cave training.
I worked alongside Nige Atkins CIC, one of the UK’s most experienced trainers and it was a pleasure to absorb his knowledge. We ran day 1 from Oaklands OEC, in their annex building, where there was a small but amply equipped training wall. This venue is a perfect base for LCMLA courses and technical training. Day 2 started with an introduction to tyrolean traverse rigging and then it was off to a local mine to put it all into practice.

LCMLA L2T Dec15 (1)

We set a 40m floating SRT line for longer spells of practice on the rope.

LCMLA L2T Dec15 (2)

Course members and Nige taking a break.

LCMLA L2T Dec15 (4)

Alun contemplating knots.

LCMLA L2T Dec15 (6)

The first day was a relaxed, candidate-led workshop environment where we managed to cover a huge amount without needing to follow a rigid plan. The candidates were a great bunch and it was nice to have a mix of other outdoor qualifications in the room.

If you are interested in becoming a BCA cave leader award holder then the first stop for you should be the BCA Training web pages. You need to register for the LCMLA scheme before Level 1 training and this registration will take you through the whole LCMLA scheme.
BCA Training Website

Pulling SPIT anchors – Back garden test

This week I thought I’d embark on a little back garden test of some brand new SPIT self driving anchors and some SPIT Grip 10mm sleeve anchors. Both take a normal M8 bolt and hanger and can be found in caves and mines across the UK. The Grip sleeves are placed with a drill and only require a 10mm hole, the caving SPIT sleeves can be placed with a hand driver or drill/driver combination in a 12mm hole. Recently there have been discussions about potentially removing superfluous spits in some committees. The idea being that any old ones could now be removed where resin bolts are installed nearby.

I made a quick trip to the Hitch N Hike emporium of shiny things and located a lump of suitably good limestone to transport to the back garden. I set a number of each SPIT anchors into the limestone using the standard installation method for each. For testing I used my freshly calibrated Hilti HAT-28 unit attached directly into the sleeves via a hardened M8 bolt.

20151102_163250391_iOS

Bolt 1, 12mm:
This didn’t make it as far as the testing. Unknown weaknesses in the boulder cracked open as I was hammering the bolt home and the placement failed. Annoying but it does serve to highlight the issues of using any expansion anchor, especially shallow ones like these. Another tick in the ‘for’ column for resin bolts.

20151102_163225670_iOS

Bolt 2, 12mm:
A normal placement in a better part of the rock. I tested this by adding force in 4kN increments until 15kN was reached and the bolt started to slowly extract from the hole. Every time the force increased beyond 15kN the bolt pulled a little further out until it ultimately was removed intact from the rock at a little over 15kN.

Bolt 3, 12mm:
A normal placement as with Bolt 2 in good rock. Force was applied in the same way as before up until about 18kN when a small cracking noise was heard. I very gently increased the load expecting the cracking might be the limestone surface under the metal legs of the puller. At 19kN the bolt let out a loud crack and the tester jumped free of the block. “Great” I thought, it pulled out. Nope. The SPIT sleeve sheared about 15mm from the top, the remainder remaining set in the limestone block.

20151102_165657454_iOS

This was a first for me and I came to a couple of possible conclusions.
1: The sleeve was defective and the break was a freak occurrence.
2: The bolt I used was not screwed far enough into the sleeve and as such mainly applied force to the top section of the sleeve.

Bolt 4, 10mm:
This anchor came out very quickly. The bolt was extracted intact at 5kN. On later inspection the internal cone had not been driven to the full depth, perhaps 6mm short of the end of the sleeve. I suspect this made for a poor expansion in the hole and hence low removal force was required.

Bolt 5, 12mm:
As for Bolt 3, this sheared in the hole, leaving over half its length still in the placement. It sheared at 20kN. I suspect that a longer bolt would give a different result for this type of test. The bolt used was tightened to the same depth as a standard hanger plate attachment would have been when in normal use. The next test would use a longer bolt.

Bolt 6, 12mm:
A longer bolt was used to test this placement. The bolt was screwed in until fully inside the sleeve but not tightened as I did not want to begin to force the cone out the back.
This test did not result in bolt failure. The sleeve was extracted 1mm from the rock as the force reached 18kN and at 20kN was still holding strong at that position. This is the maximum force the HAT-28 can apply.

Bolt 7, 10mm:
This sleeve had it’s cone driven harder when setting, to the point that the sleeve began to push into the drill hole slightly. The tester removed this bolt from the rock at 9kN and it came out intact. The cone was found to be 4mm from the end of the sleeve.

Bolt 8, 10mm:
This bolt was set very hard indeed. The cone was pushed completely into the back of the sleeve with some serious hammering force. The cone was 3mm from the back of the sleeve. This bolt was extracted at 13.5kN and came out intact. The rock around the placement failed as the bolt was nearing full extraction.

Summary:

Bolt 1 12mm no result
Bolt 2 12mm extracted at 15kN
Bolt 3 12mm sheared at 19kN
Bolt 4 10mm extracted at 5kN
Bolt 5 12mm sheared at 20kN
Bolt 6 12mm no failure at 20kN, 1mm of extraction
Bolt 7 10mm extracted at 9kN
Bolt 8 10mm extracted at 13.5kN

20151104_132413931_iOS

Conclusion
Nothing can really be drawn from that info as it is such a small sample. The main learning points I have taken from this are:

  • 12mm sleeves may shear when a bolt is not inserted fully.
  • 10mm sleeves extract at lower forces than 12mm sleeves.
  • 10mm sleeves must be driven home very well to make their higher strengths. This is not always possible as the sleeve can be pushed into the drill hole if not drilled to exact depth*.
  • All shallow expansion anchors can cause the rock to crack near the surface and no placement at this depth can be 100% guaranteed until the cone is set.
  • There are big variations in the extraction forces which depend on many variables during the installation..
  • No sleeve anchor can be removed with 100% certainty meaning that they will likely remain in the walls of the cave or mine forever.

*One of the selling points for this type of anchor sleeve is that they have a lip to prevent them slipping into over drilled holes.

I’ll be doing some further testing soon and will be taking the rig to some corroded anchors already in situ for a more real world test.
Finally, please consider not using SPIT sleeves or any other brand in places that get high traffic or will likely be resin bolted in the future. They will litter the cave wall forever (as can be seen in places like Garlands Pot and P8). A resin bolt can be removed and the hole reused. A 12mm through-bolt can be over drilled and hit into the hole and covered with resin. SPIT sleeves are likely visible forever.

Can you cut rope with a household jet washer?

After the last blog post where I tried to compare washing a caving rope in a washing machine to jet washing I thought I’d try to see how much damage I could do to a rope with a jet washer. w

This photo was from the previous test where I exposed the rope to a full power, fine jet for approximately 30 seconds.OLYMPUS DIGITAL CAMERAI could not see any evidence to say that the rope had been damaged by the jet wash exclusively. The longer fibres shown here could have been the result of the already cut fibres in the sheath (short cut sections showing) being forced out from under another braid. Of course, the damage may be down to the jet wash alone. I think the only real way to progress with this test is to take a piece of brand new rope and jet wash it. I don’t have any laying about right now so I did some more testing with the leftover Beal Antipodes 9mm from the previous testing.

I split the rope down into various grades, from single bundles to cotton size filaments.Anatomy of a ropeI hypothesis that the worst case scenario is a rope being jet washed up against a solid surface whilst under moderate tension. The tension would keep the rope in the jet longer and the solid backing would provide a surface for the fibres to be crushed against or even abraded. It had occurred to me the damage could come from the power of the jet rubbing the rope against a course material.
The backing for this test was a piece of porcelain tile, almost completely smooth to the touch. The tile sat between the rope fibre and the wood in the test device I knocked up.Test assembly v1I tested each size of bundle on both full power and the normal setting that I use for washing. Both jet setting were fired at point blank range into the fibres for 60 seconds. This test was repeated at least twice for each sample after it was checked close up.
This sample had been washed on high power/very tight jet for 120 seconds. The jet was directed at the same area of the sample for all the test time. For scale, the fibre here is about size of that very tough cotton used for stitching canvas and kit bags together.One strand

The fibre bundles became so small that I could easily break them in my hands. This one was no bigger than a piece of cotton.Cotton thinkI figured that if my jet wash could not cut through a piece of sample that was thin enough to break easily with my hands then I did not need to progress onto smaller samples.

Conclusion?

As before, I need to state that this back garden test does not give a statistically sound result and as such only serves to show what occurred in this one instance of testing.

I could not get my jet washer to cut any size of sample on this test. In both high power/confined and low power/wide spread modes, I saw no damage to the rope fibres. No doubt individual filaments of the fibres may well cut very easily but they break with the slightest of effort in the hands anyway so I doubt the value of that observation. The cotton size sample was the smallest test size and even that could be broken by hand with little effort.To guarantee no damage to any types of ropes or clothes is by using the A Plus Soft Wash services.
It is also worth noting that this experiment was done on a 7 year old rope that had seen high use in very abrasive environments over its life.

Challenge

I’d really like for other cavers to go out and try this experiment for themselves. Take a small piece of old or new semi-static caving rope and split it down to various sample sizes. Use a domestic jet washer / pressure washer on it’s highest setting and see if you can cut or damage the sample. For consistency, do it in 60 second, point blank range bursts.
Let me know via the contact address on my website or via the thread on UKCaving what happens. Failures to cut are just as important as actual cuts, so let me know either way.