Wood and Stone - A Historical Research Question

[jackstow]

Hello,
I am writing a historical novel (set in the mid-18th century) about a man who creates a stone monument. But I am stuck (and I mean STUCK) on a particular detail. I am hoping some kind forum member may be able to assist.

For the purposes of the novel, the protagonist is required to work atop a large granite boulder,60+ feet (18m) high. The boulder is free-standing, on a flat, grassy plain, but with plenty of trees available . My problem is this: How does the protagonist get to the top of the boulder in order to commence working the stone?

The obvious(?) answer would be to build a staircase. But this raises all kind of questions; i.e. how does one attach the wood supports to the granite boulder? Remember, this is circa 1760's with only the tools of the time available. I considered drilling as a possibility (whether by chisel or a period drill) but am concerned that this would only split the stone. I cannot think of another option. Also, how would the bolts attach to any drilled hole?

Can someone suggest how this might be done (i.e. attaching or securing timber to granite) bearing in mind the historical period?

I would be grateful for any suggestions.

[chambezio]

What comes to my mind is a free standing timber scaffold erected around the rock. The sculptor would have to have unimpeded access to the surface of the stone to "set out" his subject then attack it with hammers and chisels. There would have to be platforms built into the scaffold so he can have a comfortable height to do his sculpting.

[jackstow]

Hi Rod, and thanks for the prompt response to my question.

I think that your suggestion is an excellent one and one that I may have to adopt, albeit with some reluctance (purely for novelistic purposes). Unless there are some other options out there?

[BobL]

Pinning to a rock face is actually quite easy, albeit slow because of the medieval drilling processes available.

A hole is drilled to the right depth and size with a hammer and chisel using a belt and turn method - same way the poor bastards built the Thai-Burma railway.
The hole is also tapered so the inside is slightly bigger than the entry.

A piece of wood that fits the hole entryway has a shallow narrow slot cut in the end and a hardwood wedge loosely inserted into the end. Then the piece of wood is belted into the hole wedge first - the wedge splits and expands the wood inside the hole. The fastenings last for decades and even centuries.

Bolts with a screw on one end can be attached to a wooden plug inserted into the hole where the bolt itself acts as an external wedge.
The other method used if lead was available was to trap the bolt in the hole using molten lead.

[jackstow]

BobL

Re your fascinating suggestion...

Do the 'piece of wood' and hardwood wedge serve as the plug also, or does a separate piece of wood need to be inserted?

Also, given the 'medieval drilling methods' you rightly describe, would the number and depth of the holes required to support a series of wooden beams be so formidable as to render the approach impracticable--even if made via hammer and chisel? I am guessing a useful hole would need to be at least 5cm deep to anchor a support beam?

I have researched various sites in order to gauge the difficulty of drilling granite with a bow-type drill. The estimates vary wildly, from a 1/2 inch to 2 inches per hour. On the other hand, several YouTube videos appear to show posters drilling into hard stone with a hammer and chisel with minimal difficulty. But they are using modern, steel-tipped chisels. I am not sure if a forged iron chisel would perform with the same efficiency.

What are your thoughts?

[BobL]

Do the 'piece of wood' and hardwood wedge serve as the plug also

yes, the piece of wood can protrude many 10's of cm. Sometimes angle wood support braces from underneath were used with holes also drilled on the angle or simple notches cut into the stone to stop the brace from sliding.

, or does a separate piece of wood need to be inserted?

No, it can be all one piece.

Also, given the 'medieval drilling methods' you rightly describe, would the number and depth of the holes required to support a series of wooden beams be so formidable as to render the approach impracticable--even if made via hammer and chisel? I am guessing a useful hole would need to be at least 5cm deep to anchor a support beam?

The holes were probably more like 10 - 15 cm deep , depending on the side of the plug.
Most of the holes I have seen were about 10cm long and 4 cm in diameter but some were as big as 10 cm in diameter.

I have researched various sites in order to gauge the difficulty of drilling granite with a bow-type drill. The estimates vary wildly, from a 1/2 inch to 2 inches per hour. On the other hand, several YouTube videos appear to show posters drilling into hard stone with a hammer and chisel with minimal difficulty. But they are using modern, steel-tipped chisels. I am not sure if a forged iron chisel would perform with the same efficiency.

A forged iron chisel would be as good at chipping the rock but not as abrasion resistance so it would only work well for a short period before going blunt. Medieval stone masons would be able to sharpen the chisels on something like a pedal powered water stone or just have more sharp chisels on hand. Chisels cannot be resharpened indefinitely because eventually the hardened tip would be worn away and the tip needed re-hardening.

Only the tip was hardened and the shaft and stuck end left soft otherwise the chisel would shatter.

Even a small village had a blacksmithing who would resharpen and re-harden and temper chisels. A stone mason would visit the smithy once or twice a week (market day?) to get these done.

The whole business of blacksmithing is much more complex than most people realise eventually developing into a cross between science, engineering and sorcery. The village blacksmith was often considered the cleverest bloke in the village.

[jackstow]

Wow. Great info. Thank you.

As part of my research into period chisels I did a lot of reading on blacksmithing. I never realised how integral the trade was to a developing society. The blacksmith's forge was the engine that drove all other trades. Incidentally, I learned the name 'blacksmith' arose from iron being referred to as the 'black metal' together with 'smith' meaning a 'smiter' of metal.

And back to granite, again..

I had assumed that black powder (gunpowder) would be the preferred method of removing excess stone in, for example, a quarry. I was rather surprised to learn of the preference for 'drilling' as described in your post, and even heat (splitting the rock bed by lighting a fire on top and then quickly cooling and hammering the surface. Apparently, gunpowder blew up the stone, rendering it useless for steps, memorials etc.

[Fuzzie]

Given the rock is freestanding on a flat plain, why not use something mobile like a medieval rolling siege tower?

[BobL]

Wow. Great info. Thank you.

As part of my research into period chisels I did a lot of reading on blacksmithing. I never realised how integral the trade was to a developing society. The blacksmith's forge was the engine that drove all other trades. Incidentally, I learned the name 'blacksmith' arose from iron being referred to as the 'black metal' together with 'smith' meaning a 'smiter' of metal.

My mums Venetian dad, grandad and great grandad were all blacksmiths. Their surname was "Favero", which in venetian dialect means "glass maker" and is entirely consistent with their heritage.
However, it's not that far and could even have been corrupted from "Fa - ferro" which is iron maker. Probably entirely coincidental but still interesting.

I had assumed that black powder (gunpowder) would be the preferred method of removing excess stone in, for example, a quarry. I was rather surprised to learn of the preference for 'drilling' as described in your post, and even heat (splitting the rock bed by lighting a fire on top and then quickly cooling and hammering the surface. Apparently, gunpowder blew up the stone, rendering it useless for steps, memorials etc.

The other method was to drill holes and fill the holes with dry wood and then wet the wood.

RE; Seige tower
It would depend on how many friends he had to move it with.

[jackstow]

Given the rock is freestanding on a flat plain, why not use something mobile like a medieval rolling siege tower?

That would be another book

[joe greiner]

The sculptor hires an archer. The archer fires an arrow, with slender line attached, over the boulder to the other side. At the near end of the line, he attaches a slightly stouter line/rope. From the far end, he pulls the line, and thence the rope, over the boulder. He continues this process, with stouter ropes, until the final rope can support his weight and tools, perhaps even a rope ladder. He lashes a log to the far end as a counterweight. Actually, he can simply pull his tools upward with a separate rope carried aloft.

As the work progresses, he shifts the rope over the boulder. As a precaution, he might add some ropes, also lashed to logs, draped to the sides to stabilize the main rope.

Upon completion, he detaches the counterweight logs, and everything falls to earth, with some help.

On a much smaller scale, I've used variations of these elements in tree felling.

Cheers,
Joe

[jackstow]

Hi Joe.
I considered that method. Also, floating a rope over the boulder via a kite. But I think I am going to go with the scaffold/pinning methods discussed above.
Thanks for the contribution.

[swk]

Hello,
I am writing a historical novel (set in the mid-18th century) about a man who creates a stone monument. But I am stuck (and I mean STUCK) on a particular detail. I am hoping some kind forum member may be able to assist.

For the purposes of the novel, the protagonist is required to work atop a large granite boulder,60+ feet (18m) high. The boulder is free-standing, on a flat, grassy plain, but with plenty of trees available . My problem is this: How does the protagonist get to the top of the boulder in order to commence working the stone?

The obvious(?) answer would be to build a staircase. But this raises all kind of questions; i.e. how does one attach the wood supports to the granite boulder? Remember, this is circa 1760's with only the tools of the time available. I considered drilling as a possibility (whether by chisel or a period drill) but am concerned that this would only split the stone. I cannot think of another option. Also, how would the bolts attach to any drilled hole?

Can someone suggest how this might be done (i.e. attaching or securing timber to granite) bearing in mind the historical period?

I would be grateful for any suggestions.

How many people are involved in this work?
If it isn't many, then there is a lot of work making a scaffold. Some sort of ladder might be the go. Considering the novel date is mid 1700s, dont underestimate how sophisticated society was then anyway. I have seen ladders mounted on carts used in old European cathedrals for (I assume) cleaning the high windows etc. They would probably reach 60'.

Also, depending on the thing being carved, part of the work itself could be a platform cut into the rock, starting from the top down. The platform disappears as the sculpture progresses. This isnt a good description by me, but it is how some people think the carving at Petra was done.

Blacksmiths:
I read an article once on the construction of one of those lighthouses on a little rocky island off the UK coast. Basically had a full time blacksmith repairing and sharpening tools as part of the work team.

SWK

[swk]

IMG_1136.JPG Here's one. Scaling it off the chairs, I would say this is a 50' ladder.
All your sculptor has to do is borrow one from the nearest* big church.

*yeh, that could be lots of miles away, but still easier than chopping down trees and making a scaffold.

SWK

[BobL]

Here's one. Scaling it off the chairs, I would say this is a 50' ladder.

I doubt it
1. there are 22 steps in total. so each step would have to be 2.4ft apart.
Ladder steps are typically 1ft apart so that ladder is less than 25ft.
2. I also put the photo into photoshop and using pixel counts worked out that the chairs have to be 8.5ft tall for that ladder to be 50ft tall.

Besides ladders are a mongrel to work from for long periods which is why builders (old and today) build scaffolds even for simple work.