Update 4 restoration mausoleum

Following the update of January 31, churchwarden Rien de Graaf sent the secretariat another update on July 17 on the restoration of the mausoleum in Stavenisse Reformed Church. The following is the report from Erik Jan Brans, one of the restorers:

Wednesday 31 January: continued with the foundation of the tomb and back wall, preparations for the reinforced concrete floor.

Thursday 1 February: continuing with the foundations of the tomb and back wall.

Tuesday 6 February: continued with the foundation of the tomb and back wall.

Thursday 8 February: continued with the foundation of the tomb and back wall.

Friday 16 February: continued with the foundation of the tomb and back wall.

Monday 19 February: cleared for church restoration i.e. erection of scaffolding etc.

Tuesday 20 February: floor under tomb fitted with screed.

Wednesday 21 February: meeting in Amsterdam in Tobias Snoep’s studio.

Had what I think was a useful meeting today. Here are the main points:

• A beautiful rinsing installation has been built with 2 trays of marble pebbles, an ion filter and a large insulated tray for the parts, equipped with a dipper with thermostat. The monument will require 4 batches.
• Temperature is controlled between 19.5 and 20.5 degrees C.
• Some parts of the pilasters of the back wall have been in the bath for a few weeks now. They lie on 6 cm foam blocks and the water level is slowly being raised. Now the blocks are about 2 cm in the water. Water is tap water with a conductivity of approx. 520, in the tank a conductivity of approx. 1100 is already measured. This conductivity varies slightly, but it very much looks like salt is now coming out of the marble anyway. This is strange, because all tests show a very low amount of salts. Those tests were carried out by Rob Crevecouer, TU Delft and Nebest. We didn’t address this issue, but is it an idea to have both a sample of tap water and water from the tank tested? Then it can be determined which substance is causing the increase in conductivity.
• The front plate was also (virtually) saltless according to Nebest’s research. Theoretically, it could go to IBACH in no time. I find the already rapid increase in conductivity, while we haven’t even begun flushing yet, worrying in relation to the front plate. If the image of the pilasters and the front plate match, there would (could) be salt in there. Question is why this was not measured then. Ten samples were taken and so the coincidence of drilling exactly in low values would be very coincidental. There is a risk in this. If there is too much salt, the process could go wrong. After discussion, it was suggested, after the first batch with the pilasters, to first put the front plate alone in the bath and wet it slowly. To do this, mortar residue will be removed from the back and the slab will be placed on its back. So the water will first moisten the inner surface. It is checked whether this also causes the conductivity of the water to rise again and thus indicates the presence of salts. If the conductivity does not increase significantly, there is nothing wrong. If it does increase then a decision has to be made on how to proceed. In any case, consultation with IBACH, but do we dare to go ahead with flushing if it does turn out to contain salt?
• It is proving difficult to determine how much water has already penetrated the parts currently in the bath, so as a matter of caution the flooding is very slow. The capillary line, as Tobias calls it, is difficult to see. The stone surface is rough and mottled. It has now been considered to add an extra white marble block in the bath that might indicate more clearly how far the infiltration has progressed. A marble block containing a hole and a float was considered. The underside of the block around the borehole should then be watertight, so that the block fills mainly from the sides and not directly into the borehole. The float then indicates the height of the water level in the block. This will not be deployed for some time yet; it will first be checked whether the block described above gives sufficient indication.
• It has not yet been agreed in detail what, how and whether damages will be repaired. Kemperman has been asked to indicate the damages on a photo, after which it can be decided what will and will not be repaired. Kemperman also makes a proposal on how the damages can be repaired and with what material. This use of materials should be coordinated with IBACH.
• There are still a number of blocks for which it needs to be determined whether or not they should be bathed. Proposal is that Hendrik does that selection.

Thursday 22 February: floor under tomb finished and back wall primed for finishing.

Friday 23 February: floor under tomb partly lined with lead.

Monday 26 February: continued with lining floor.

Tuesday, 27 February: continued with lining floor.

Thursday 29 February: start with covering rear wall with EPDM.

Monday 4 March: continuation of rear wall cladding.

Tuesday 5 March: removal of stored marble parts in church due to restoration work on church building.

Thursday 7 March: last marble parts cleared.

Friday 8 March: start restoring the black blocks of the skirting boards and slabs of the back wall.

After a very dynamic process, the first pieces are being taken out today. They are pilasters from the back wall. Just a very abbreviated short resumé of the process so far and an update:

• Pilasters put into bath first and slowly raised water level to achieve full saturation
• Despite the fact that hardly any salt was found in boreholes, the conductivity of the water increased very rapidly indicating the presence of salts. This was not expected.
• Conductivity increased so rapidly that it soon reached the limit value and the water had to be replaced even at a height of a few centimetres.
• Analyses indicated a presence of (sulphur-containing) compounds in and on the surface that leached out. Molecules in the water point to plaster deposits.
• Decided that it does not make sense to pursue full saturation because the core is not saline. Instead, decided to quickly submerge the blocks completely and closely monitor the course of conductivity. Once it stabilises, change the water. Just before changing, take water samples to see if there is also a gradient in the substances present in the rinse water.
• Repeat this rinsing process until the conductivity (flat) is close to tap water.
• Then let the blocks air dry.

As little water will have penetrated the stone due to rapid rinsing, little moisture transport from inside to outside is expected to take place during drying. This and because the salt load on the core of the blocks is low to very low, it is expected that no or very little salt will manifest on the surface when drying. That is my expectation, but we have had surprises before.
Because this method of rinsing is much faster than full saturation, the remaining lead time of the project is expected to be quite a bit shorter. This means that the very time-intensive restoration and consolidation of the front plate will suddenly be in the critical path. We must now decide whether we dare to start rinsing the front plate first in a moment so that it can be restored and IBACHTed.

Monday 27 May: continue restoring the black blocks of the skirting boards and plates of the back wall.

Tuesday 28 May: continue restoring the black blocks of the skirting boards and plates of the back wall.

Wednesday 29 May: in Amsterdam to collect the first parts de-salted from the pilasters to Stavenisse.

Monday 3 June: started masonry up rear wall, this should be to the same height as the top of the tomb.

Tuesday 4 June: continue bricklaying.

Friday 7 June: continue bricklaying.

Sand-lime

Yesterday I discussed with Tim my reluctance to apply sand-lime . I don’t know the material as a material used in restoration. To make sure it cannot cause problems in the future, I thought we should take a critical look at it. After the conversation yesterday, Tim sent me a sketch of how he saw the construction of the back wall and a description of the production process and ingredients for making sand-lime.

Sand-lime is produced through the reaction of quicklime with sand using steam under high pressure. The material therefore consists of slaked lime and sand. No harmful substances that could cause problems in the future should therefore be able to leach from this. @Hendrik: Do you know of any studies on this aspect?

The sand-lime rear wall is detached from the rear façade with a cavity several centimetres wide. The inside of the façade is covered with EPDM foil. Anchors going through the foil are sealed all around. The black marble cladding will stand loose in front of the sand-lime back wall and only make contact through their anchors. In case of any leaking out of the sand-lime, this will not burden the monument because of the cavity. Differences in thermal expansion will also do little harm, especially since the temperature follows outside temperature fluctuations very cushioned and everything is spaced with anchors.

Other than an instinctive aversion to the material, I have no rational reason to doubt the applicability of sand-lime at the moment.

• Lead has been installed under the site of the bier.
• Some pieces of black marble are heavily corroded. Here, parts have flaked off about 1cm deep. These are precisely pieces that are quite visible. Need to discuss what to do with them.
• The front plate is now in the bath. Then it has to be dried and restored. For that, we need to decide how far to go with it. After that, it has to go to IBACH. I can see that the front plate will not be back in time before it should actually have been set. In order not to let the work stagnate, it is worth considering how the rest of the monument can be built up independently of the front plate so that it can be put in place later.
• Tim makes a work plan for putting the monument back in place based on the latest findings.

Monday 10 June: continue bricklaying.

Tuesday 11 June: continued bricklaying now finished to height of tomb.

Thursday 13 June: first black plinth put back in place.

Monday 17 June: meeting via Teams.

Thursday 20 June: preparations for placing back the black boards above the black skirting boards against the back wall.

Monday 24 June: preparations for refitting the black boards above the black skirting boards against the back wall.

Thursday 27 June: preparations for refitting the black boards above the black skirting boards against the back wall.

Monday 1 July: first plate fixed with wall anchors against the back wall.

Tuesday 2 July: second plate fixed with wall anchors against the back wall.

Thursday 11 July: preparations for skirting boards above the black boards.

Friday 12 July: skirting boards fixed.

Monday 15 July: rear wall to top further covered with EPDM.

Tuesday 16 July: two white pilasters placed on right side.

Wednesday 17 July: black large plate to hang coats of arms placed on right side.

SUMMER HOLIDAY

Photos of the progress can be found here.