Conservation studies of the ruins of the Gothic Kazimierz castle (2nd half of the 14th century) in Koło (Gozdów)

Piotr Niemcewicz, Katarzyna Polak, Aleksandra Gralińska-Grubecka,Karolina Witkowska, Wojciech Bartz, Marta Chylińska, Andrzej Podgórski

doi:10.37190/arc220406

Abstract

The purpose of this article is to present the conservation research carried out as part of the revitalization project of the ruins of the castle in Koło. Basis of the recognition of the monument’s construction technique, identification and determination of the properties of historical and contemporary materials, assessment of the state of preservation and analysis of destructive factors developed a program of conservation works. Research was carried out considering the findings of architectural research. Laboratory tests of the collected material were carried out by a wide team of employees using specialized research techniques. Their results are presented in this article and include petrographic, chemical and thermogravimetric analyses of mortars, rocks and bricks, their capillary and mechanical properties, salinity analysis and microbiological analyses of materials. The undeniable value of the conducted research is a detailed diagnosis of historical building materials, which is a significant contribution to the knowledge of old construction techniques.

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2022

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Piotr Niemcewicz*, Katarzyna Polak**,

Aleksandra Gralińska-Grubecka***, Karolina Witkowska****,

Wojciech Bartz*****, Marta Chylińska******,

Andrzej Podgórski*******

Conservation studies of the ruins of the Gothic Kazimierz castle

(2

nd

half of the 14

th

century) in Koło (Gozdów)

Introduction

The ruins of Gozdów castle (Fig. 1) have been of interest

to historians and researchers for many years. Recently, the

Koło district

1

, as the owner of the object, has started prepa-

rations for the development project of the ruins along with

the surrounding area, intended in the long term for a com-

munal recreation and cultural centre [1]. In 2019, archaeo-

logical research was resumed [2] and architectural [3] and

* ORCID: 0000-0003-4123-5319. Department of Conser-

vation and Restoration of Architecture and Sculpture, Nicolaus Coperni-

cus University in Toruń, Poland.

** ORCID: 0000-0002-7400-5037. Department of Conser-

vation and Restoration of Architecture and Sculpture, Nicolaus Coperni-

cus University in Toruń, Poland.

*** ORCID: 0000-0002-7566-4747. Department of Conser-

vation and Restoration of Architecture and Sculpture, Nicolaus Coperni-

cus University in Toruń, Poland.

**** ORCID: 0000-0003-4363-1542. Department of Conser-

vation and Restoration of Architecture and Sculpture, Nicolaus Coperni-

cus University in Toruń, Poland.

***** ORCID: 0000-0002-7267-2776. Faculty of Earth Scienc-

es and Environmental Management, Institute of Geological Sciences,

University of Wrocław, Poland.

****** ORCID: 0000-0002-2188-6950. Department of Conser-

vation and Restoration of Architecture and Sculpture, Nicolaus Coperni-

cus University in Toruń, Poland, e-mail: mch@umk.pl

******* ORCID: 0000-0003-3678-3732. Department of Conser-

vation and Restoration of Architecture and Sculpture, Nicolaus Coperni-

cus University in Toruń, Poland.

1

The presented article was developed on the basis of [1]. The research was

carried out in the period May–October 2021 at the request of the Koło district.

conservation research [4] was ordered

2

. Research on build-

ing materials of strongholds in Poland has already been the

subject of analyses [5]–[8], but still require continuation.

The purpose of this article is to present the results of

the works carried out as part of the revitalization project

of the ruins of the castle in Koło. Conservation research

conducted at the castle in Koło made it possible to identi-

fy building materials: mortars and bricks in terms of their

composition, determine their properties as well as assess

the state of preservation and identify the causes of dam-

age. Material delamination was analysed in situ, the state

of preser

vation was thoroughly assessed by classifying, de-

scribing and documenting individual types of damage, sam-

ples were taken for testing along with documentation of the

sampling sites. Laboratory tests of the collected materials

included chemical analysis of mortars, testing of compres-

sive strength, petrographic analysis of bricks and mortars,

thermogravimetric analysis, qualitative and quantitative

analysis of soluble salts and microbiological analysis of

damaged bricks, granulometric analysis of mortar fraction

unreacted with HCl, determination of pH, capillary proper-

ties of materials, including eective porosity, water absorp-

tion by weight, capillary rate. The results of these

studies

2

The purpose of conservation research in accordance with the

Usta wa z dnia 23 lipca 2003 r. o ochronie zabytków i opiece nad zabyt-

kami [Act on the protection and care of monuments of July 23, 2003] [4,

art. 3, point 9] is to identify the history and functions of the monument,

to determine the materials and technologies used to build it, to determine

the state of preservation of this monument and to develop a diagnosis,

project and program of conservation works.

DOI: 10.37190/arc220406

Published in open access. CC BY NC ND license

60 Piotr Niemcewicz, Katarzyna Polak, Aleksandra Gralińska-Grubecka et al.

as well as the results of the architectural research, became

the basis for developing a program of conservation works.

Historical outline

The castle was the seat of Koło district governor and

secured the road leading from Wielkopolska towards

Łęczyca through the Warta valley. It was erected on the

southern bank of the river, on an articial hill. The strong-

hold is mentioned for the rst time in 1383 in the chronicle

of Janek of Czarnków as the seat of the district governor

– Krystyn of Koziegłowy [9, p. 625]. According to Jan

Długosz, the construction of the castle was connected

with the building action of Kazimierz Wielki, thus listed

it among other castles and mansions founded by the ruler

before 1370 [10, p. 441]. The condition of the castle deteri-

orated relatively quickly, because in 1507 the district gov-

ernor of Koło donated 500 orins for its restoration [11],

and at the end of the 16

th

century the castle was

already

in ruins. In the interwar period, only basic security works

were carried out [12]. In 1953, the ruins of the castle were

entered in the register of the monuments. At that time, an

inventory was made as well as protection and conserva-

tion works were carried out within the curtain walls and

the southern corner of the tower. Conservation work was

resumed in 1971 and 1987, and the last one was carried

out at the beginning of the 21

st

century [11]. Archaeologi -

cal works have been conducted in the castle since 2019.

Construction technique of walls

The walls of the castle in Koło were erected using ma-

terials traditionally used in the Middle Ages, available lo-

cally such as natural stone, brick, lime mortar and river

sand. Brick, stone, lime and lime-cement mortars were

also used in the repairs.

Rocks – natural stone

Erratic blocks were used to build the stone wall. In the

preserved original parts of the wall, large boulders were

layered, and smaller pebbles or keels were used to ll

voids or level the layer. Wall repairs made later dier in

the size of the pebbles, the method of their masonry and

the mortar face. They were mostly arranged randomly, and

bricks were used to ll the voids between the large boul-

ders. The exception is the rebuilt south-western corner of

the base of the tower, where the boulders were arranged

in layers, imitating the pattern of the historical stone wall.

Sandstone blocks from Brzeźno

3

[13] (Fig. 2) were also

used for the repair of the plinth, probably coming from the

ruined parts of the residential tower. This is indicated by

the type of material and similar dimensions and method

of processing.

In the preserved parts of the residential tower, cuboid

squares of irregular dimensions are arranged in layers,

forming the facing of opus emplectum. Blocks of stone

have a smooth surface or traces of hammering or pointing.

Brick

The walls of the castle were built of properly red bricks.

There are few zendra bricks distinguished by a black-grey

colour and slight glazing induced by very high tempera-

ture in the kiln. On the cylinder of the tower, they are form

a “diaper work”. On other elevations they are sporadic

and randomly built.

On the basis of petrographic research, for which var-

ious bricks from phase II of the castle construction were

selected

4

, many common features were found as the com-

3

It is a Miocene (formerly Tertiary) quartzite sandstone. It is charac-

terized by a very high quartz content (over 95%), hardness and high me-

chanical strength. It has a gray color of varying intensity. From the early

Middle Ages, it was used in the architecture and sculpture of Wielkopolska.

4

Chronological stratication based on architectural research (M. Pra-

rat, U. Schaaf) showed two construction phases: I (3

rd

quarter of the 14

th

century) and II (3

rd

quarter of the 15

th

century) divided into 9 stages and

three successive phases III, IV, V relating to repairs.

Fig. 1. Castle in Koło. A tower and a fragment of the western wall

(photo by K. Witkowska, 2020)

Il. 1. Zamek w Kole. Wieża i fragment muru zachodniego

(fot. K. Witkowska, 2020)

Fig. 2. Castle in Koło. Fragment of a buttress with a restored boulders

faced wall with sandstone blocks (photo by K. Polak, 2020)

Il. 2. Zamek w Kole. Fragment przypory z przemurowanym kamiennym

licem z użytymi blokami piaskowca (fot. K. Polak, 2020)

Conservation studies of the ruins of the Gothic Kazimierz castle (2

nd

half of the 14

th

century) in Koło (Gozdów) 61

Fig. 3. Castle in Koło. An exemplary sample of medieval mortar

(elaborated by K. Witkowska, 2020)

Il. 3. Zamek w Kole. Przykładowa próbka średniowiecznej zaprawy

(oprac. K. Witkowska, 2020)

position of the grain skeleton is dominated by quartz,

next to which feldspar and grains of (crystalline) rocks.

The accessory components are oxyhornblende, muscovite

akes, opaque minerals. In both samples, the morphology

of the skeleton grains is similar, those with sizes below

0.2 mm predominate, and grains of about 0.8 mm are rare.

The matrix is quite heavily sintered, mainly aphanitic with

occasionally visible relics of clay minerals. A character-

istic feature of the samples is a relatively signicant vol-

umetric share of skeleton grains, with a relatively small

share of sintered (meta)clay matrix as well as the pres-

ence of characteristic, small brownish-black aggregates.

These are presumably clasts of the original clay raw ma-

terial, unhomogenized with the ceramic paste, enriched in

Fe-beraing minerals.

Tests of mechanical properties

5

showed negligible dif-

ferences. Bricks from phase I were characterized by com-

pressive strength in the range of 3.6–4.8 MPa, and from

phase II from 3.6 to 4.1 MPa.

Bricks in both historical building phases indicate simi-

lar capillary features (Table 1)

6

.

Historical mortars

The original mortars assigned to phases I and II of the

castle erection exhibit similar petrographic characteris-

tics (Fig. 3). The composition of the grain skeleton of all

samples is dominated by quartz, while feldspars and rock

grains are rare. Accessory components are represented

by amphibole and opaque minerals. The morphology of

grains in all samples is similar. The grains are similar in

size, do not exceed 1.0–1.2 mm, and exhibit a good and

very good roundness. Very ne aggregates, with a diame-

ter below 0.5 mm, dominate (Table 2).

Interesting in the aspect of historical construction tech-

niques are the results of analyses on the mortar binder.

On the basis of the petrographic analysis, it was found

that carbonate binder (micrite) was present in all exam-

ined samples, but it shows some dierentiation. Lime

lumps (micrite aggregates) isolated from the binder mass

5

The tests were performed using the ToniPRAX 1543 hydraulic

press from Toni Technik Baustoprüfsysteme GmbH (measuring range

3–300 kN); control of hydraulic press and processing of results was car-

ried out using the testXpert software.

6

Water absorption and eective porosity of the samples were de-

termined using the OHAUS PX523m/1 balance, equipped with a density

determination kit.

were observed in all of them. They are clearly smaller

in size, sometimes containing ne grains of quartz with

glassy rims. Occasionally, apart from typical lime lumps,

the other binder-related, i.e., silicate sinters (overburned

lime lumps) formed during the calcination of lime from

carbonate raw material containing silicate components

(clay minerals or the aforementioned ne-grain quartz)

are found (Fig. 4). The occurrence of structures such as

silicate sinters in mortars or the presence of ne grains of

quartz grains in lime lumps may suggest that the lime was

calcined from carbonate raw material containing signi-

cant admixtures of silicate components, i.e., quartz, clay

minerals or iron minerals. Their presence may indicate la-

tent hydraulic properties of the lime.

The results of thermal analysis

7

also conrm the latent

hydraulic properties of the binder. It was found (Table 3)

that the content of carbonates in the analysed samples

7

The analysis was performed using a thermal analyzer STA 6000

produced by Perkin Elmer; in the temperature range: 30–1000°C; heat-

ing rate of 10 °C/min; N

2

inert gas ow 20 ml/min.

Dating

Water absorption

[m/m %]

Effective porosity

[%]

Water capillary rate up to 3 cm

[min]

Phase I, 3

rd

quarter of the 14

th

century

13.32 24.57 6

12.96 22.80 7

Phase II, stage 1, 2

nd

quarter of the 15

th

century 14.15 25.39 9

Table 1. The results of the study of the capillary properties of historical brick (elaborated by A. Podgórski, M. Chylińska)

Tabela 1. Wyniki badania właściwości kapilarnych historycznej cegły (oprac. A. Podgórski, M. Chylińska)

62 Piotr Niemcewicz, Katarzyna Polak, Aleksandra Gralińska-Grubecka et al.

ranged from 10 to 34 wt.%. Therefore, it is relatively

low, which indicates the abundance of silicate ller in the

binder. In addition, the samples are characterized by low

values of CO

2

/H

2

O ratios, which is characteristic of mor-

tars with a lime binder, showing hydraulic properties [14].

However, it should be noted that in several of the analysed

samples, in the range in which the hydrated hydraulic

components undergo thermal dissociation, other physical

or chemical changes occur simultaneously, which results

in overlapping weight-loss eects. The obtained values

may be inuenced, for example, by the presence of clay

minerals or FeOOH. Therefore, some values may be ac-

companied by a greater measurement error.

Based on the chemical analysis, commonly used to

determine the proportions of the reacted and unreacted

with hydrochloric acid components of the lime mortars,

it was found that the proportions of the carbonate binder

and silicate ller fall within a fairly wide range, mostly

between 1:1.4 and 1:2.5. For several mortars, proportions

>1:3 were determined. Chemical and macroscopic anal-

ysis conrm the hydraulic nature of the mortars (Fig. 5).

A large dierence in the proportions within the analysed

samples assigned to individual construction phases does

not have to result from intentional action. It may indi-

Filler fraction [mm]

above 1.6 1.6–1.0 1.0–0.5 0.5–0.315 0.315–0.2 0.02–0.071 below 0.071

Table 2. Exemplary distribution of the aggregate fraction of the mortar from phase II (elaborated by A. Gralińska-Grubecka)

Tabela 2. Przykładowy rozkład frakcji kruszywa zaprawy z II fazy (oprac. A. Gralińska-Grubecka)

Fig. 4. Castle in Koło. Close-up of the mortar in the joint with visible

fragments of calcined limestone (photo by K. Polak, 2020)

Il. 4. Zamek w Kole. Zbliżenie zaprawy w spoinie z widocznymi

okruchami kalcynowanego kamienia wapiennego (fot. K. Polak, 2020)

cate carelessness of contractors or imperfect production

technology. This conclusion is conrmed by in situ obser-

vations. In many places, lumps and crumbs of binder of

various sizes and shapes are visible on the fractures of the

mortar. They occur irregularly, occasionally in clusters.

Another reason for the large discrepancy in ller-bind-

er proportion may results from the heterogeneity of the

lime rock used to make the calcine binder. Small outcrops

of carbonate rocks of Cretaceous age occur in the vicinity

of Koło. They are dominated by marls, marly limestones,

and less common limestones, which could have been used

as a raw material. These rocks, apart from calcium car-

bonate, contain magnesium carbonates and clay minerals,

detrital grains, in various proportions. As a raw material,

calcareous gyttja could also be used. It is a common sed-

iment in ribbon lakes (for example the Lake Gopło), con-

taining, apart from organic matter and calcium carbonate,

also minor clastic components and clay minerals.

The proportions of mortar components determined

in

laboratory tests, due to the presence of hydraulic com-

pounds, do not reect the proportions of mortar compo-

nents understood as the ratio of binder to aggregate, which

is usually the basis for developing mortar recipes for ren-

ovation works. For the proper selection of mortars for the

planned works, it is equally important to determine the capi-

lla ry properties and mechanical strength of the materials.

The determined eective porosity of historical mortars

(Table 4) ranges from 22.9 to 34.8%, usually around 30%.

Water absorption by weight is relatively high – it ranges

from 12.9 to 22.9%. It should be emphasized that the mor-

tars from phase I show both the highest porosity (34.8%)

and water absorption (22.9%). Large dierences in the rate

of capillary rise can be explained by the heterogeneity of

the mortars used for the tests, because the largest possible

to obtain fragments, heterogeneous in nature, were tested.

A large dispersion of results was obtained in the study

of the mechanical properties of mortars (Table 5). The

possibility of obtaining only small-volume samples with

the above-mentioned heterogeneity of mortars and the

standard requirements of the testing equipment used, lim-

ited the number of tests performed. The determined com-

pressive strength of mortars is very high, ranging from

slightly more than 3.7 to 12.0 MPa. The average value is

about 7 MPa.

Conservation studies of the ruins of the Gothic Kazimierz castle (2

nd

half of the 14

th

century) in Koło (Gozdów) 63

Weight loss in the temperature range [%] Component content [wt.%]

Sample/ Dating 30–120 200–600 600–1000

Calcium

carbonate

Other (thermally inactive)

components

CO

2

/H

2

O

16/Phase I 0.084 1.312 7.244 16.47 83.44 5.53

19/Phase I 0.120 a 11.406 25.94 73.94 a

36/Phase I 0.563 2.857 4.358 9.91 89.53 1.53

38/Phase I 0.629 1.997 12.517 28.47 70.91 6.27

2/Phase II, step 1 0.181 a 14.763 33.57 66.24 a

5/Phase II, step 1 0.525 2.101 7.633 17.36 82.12 3.63

10/Phase II, step 6W 0.138 a 7.962 18.11 77.02 a

12/Phase II, step 7W 0.094 a 8.096 18.41 81.50 a

P3/Phase II, step 1 0.053 a 6.749 15.35 84.60 a

P10/Phase II, step 2 0.252 a 11.667 26.53 69.27 a

P12/Phase II, step 8W 0.114 a 8.343 18.97 75.13 a

P15/Phase II, step 9W 0.115 a 7.857 17.87 78.08 a

34/Phase II, step 1 0.525 1.785 9.959 22.65 76.83 5.58

35/Phase II, step 1 0.317 1.762 5.858 13.32 86.36 3.33

41/ Phase II, step 1 0.043 0.804 5.914 13.45 86.51 7.36

8/Phase III 0.028 0.959 6.190 14.08 85.90 6.46

39/Phase IV 0.269 1.356 6.083 13.83 85.90 4.49

40/Phase V 0.178 1.743 10.333 23.50 76.32 5.93

Table 3. Results of thermogravimetric analyses (elaborated by M. Chylińska)

Tabela 3. Wyniki badań termograwimetrycznych (oprac. M. Chylińska)

a – overlapping weight-loss effects make it difficult to determine the amount of water in hydraulic components.

Fig. 5. Exemplary sample

documentation:

1 – sample, 2 – break mortar,

3 – aggregate and residues

after HCl reaction,

4 – magnification of

an underburned lump of

calcined limestone

(photo and elaborated

by K. Witkowska, 2020)

Il. 5. Przykładowa dokumentacja

próbki: 1 – próbka,

2 – przełam zaprawy,

3 – kruszywo i części

nierozpuszczalne w HCl,

4 – zbliżenie grudki kalcynowanego

kamienia wapiennego

(fot., oprac. K. Witkowska, 2020)

64 Piotr Niemcewicz, Katarzyna Polak, Aleksandra Gralińska-Grubecka et al.

Presumably, both original and secondary renders have

been preserved on the arches. The mortar samples have

not been studied due to lack of access.

In addition to the described primary building materials,

in very small areas of the face of the wall, a fragmentary

red painting layer was observed, which in the past could

have been a layer unifying the façade. It is very well bond-

ed to the substrate and does not form a clearly separated

coating.

Preservation state

The preserved walls of the castle in Koło are everlast-

ing ruin and will be maintained in this form for the fu-

ture. The analysis of the state of preservation was aimed

at identifying changes and damages that may pose a threat

to the materials and currently or in the long term may

threaten the durability of both individual materials and the

structure of the wall, i.e., the entire building.

Modern mortars

Modern mortars were used as masonry mortars in parts

made in the 20

th

century and as mortars to ll mortar loss-

es in the joints of a brick wall (occasionally) and a stone

wall (in many places). Based on macroscopic observation,

several types diering in structure, cohesiveness, colour

and type of ller were identied.

Most of the examined mortars are characterized by ce-

ment and cement-lime binders. The capillary properties of

the mortars (Table 6) are various, however, sucient from

the conservation point of view. These mortars transport wa-

ter faster, due to their high porosity and aggregate content.

Renders

The renders cover the arches of the window openings in

the top storey of the tower. Based on observations, it can

be concluded that they are not the same on all surfaces.

Table 4. Test results of capillary properties of exemplary historical mortars (elaborated by A. Podgórski, M. Chylińska)

Tabela 4. Wyniki badania cech kapilarnych przykładowych zapraw historycznych (oprac. A. Podgórski, M. Chylińska)

Dating

Water absorption

[m/m %]

Effective porosity

[%]

Water capillary rate up to 3 cm

[min]

Phase I, 3

rd

quarter of the 14

th

century

22.85 34.80 34

15.88 29.62 60

Phase II, stage 1, 2

nd

quarter of the 15

th

century

15.25 26.91 3

12.93 22.93 23

16.73 28.62 15

14.58 25.12 26

20.92 33.14 20

17.79 29.05 106

Table 5. Results of the compressive strength test of historical mortars (elaborated by A. Podgórski)

Tabela 5. Wyniki badania wytrzymałości mechanicznej zapraw historycznych (oprac. A. Podgórski)

Dating

Compressive strength

Value range

[MPa]

Average value

[MPa]

Coefficient of variation

[%]

Phase I, 3

rd

quarter of the 14

th

century 3.7–6.4 5.4 19

Phase II, stage 1, 2

nd

quarter of the 15

th

century 5.1–12.0 8.8 27

Dating

Water absorption

[m/m %]

Effective porosity

[%]

Water capillary rate up to 3 cm

[min]

Phase III, 1

st

half of 20

th

century 18.83 30.91 8

Phase IV, 2

nd

half of 20

th

century 13.28 24.67 32

Phase V, early of 20

th

century 15.05 27.21 5

Table 6. Test results of capillary properties of modern mortars (elaborated by A. Podgórski, M. Chylińska)

Table 6. Wyniki badania cech kapilarnych zapraw współczesnych (oprac. A. Podgórski, M. Chylińska)

Conservation studies of the ruins of the Gothic Kazimierz castle (2

nd

half of the 14

th

century) in Koło (Gozdów) 65

Brick wall

Due to the raised level of the courtyard, the stone ped-

estal of the western wall and the northern part is covered

with soil in along its entire length. A similar situation oc-

curs within the relics of the southern wall. Direct contact

of the brick wall with the soil is often the reason of high

moisture content, but during the tests (May–October) no

clearly increased level of moisture in the structure of the

walls in the ground oor was found. In several places,

damage caused by salt crystallization was noted. Tests

conrmed the amount exceeding the permissible stan-

dards (about 4%; 6.2%) [15]

8

.

Historical brick wall

– from the first two building phases

The original face is preserved on most of the surface of

the wall. However, on large stretches, the face layers of the

wall became loosened, presumably as a result of the crack-

ing of the perpends. In many places, the face has been re-

constructed, but large losses are still present on the south-

ern wall, parts of the northern one and in many smaller

places. The facings on the buttresses are in poor condition.

Colonies of microorganisms present in various amounts

on most surfaces do not provide a direct danger to the fa-

cility. Indirectly participating in the circulation of mat-

ter, they contribute to the formation of organic deposits

that favour the colonization of walls by higher organisms

– herbaceous and woody plants. Their growth on the walls

8

The degree of salinity of the samples was determined by the con-

ductometric method using the CPC-411 device by Elmetron. The quali-

tative and quantitative composition of the aqueous sample extracts was

determined using the EA102 capillary electrophoresis apparatus (Villa

Labeco, Slovakia).

is dangerous, primarily due to the mechanical action of

the roots.

Grati as well as numerous signatures and initials en-

graved in bricks, especially numerous on the walls from

the side of the courtyard, should be mentioned as another

damage that did not signicantly aect the state of preser-

vation, but negatively changed the appearance of the wall

(Fig. 6). The painted inscriptions disturb the perception of

the monument and, despite a certain cultural value, should

be treated as an act of vandalism and removed.

A major conservation and restoration problem is the

state of preservation of the bricks (Fig. 7). Most of their

face has not been preserved. Its destruction is most often

the result of washing out or shedding of the surface layer.

In many places, the cavities form depressions and niches,

sometimes covering the entire volume of the brick. They

are visible from a distance as soft-edged cavities. It has

been assumed in the literature that this type of damage is

associated with the presence of nitrifying bacteria, which,

as a result of metabolism, produce acids capable of de-

composing rock-forming minerals (aluminosilicates in this

case). Damage initiated by bacteria is magnied and inten-

sied by the action of other factors, e.g., wind. The con-

ducted microbiological tests did not conrm the excessive

content of nitrifying bacteria on the surface of the damaged

bricks

9

, but their slow and long-term eect is possible.

Shreds, forging and similar places are in destruct con-

dition. These areas are dominated by damaged, irregular-

ly cracked and crumbled bricks bonded with mortar that

is crumbled, uneven, with many depressions, voids, etc.

(Fig. 8).

9

Microbiological tests were performed at the Department of Envi-

ronmental Microbiology and Biotechnology of the Nicolaus Copernicus

University in Toruń by Maria Swiontek-Brzezinska, PhD, DSc.

Fig. 6. Castle in Koło.

The inner side of the western

wall with numerous graffiti

and complemented bricks

on the wall face. The softly

ending crown of the breast wall

is noteworthy

(photo by K. Witkowska, 2020)

Il. 6. Zamek w Kole.

Wewnętrzna strona muru

zachodniego z licznymi graffiti,

uzupełnieniami lica. Uwagę

zwraca miękko zakończona

korona przedpiersia

(fot. K. Witkowska, 2020)

66 Piotr Niemcewicz, Katarzyna Polak, Aleksandra Gralińska-Grubecka et al.

The face of the historical bricks is covered with un-

evenly dark, thin layers well bonded to the ceramics. Be-

sides to the unfavourable aesthetical appearance, they do

not have a destructive eect on the brick.

Historical mortars are mostly in good condition, hard

and cohesive. In many places they are preserved with the

paths of masonry tools on the surface. The damage that

occurred – slight washing out at the edges, legibility of

gaps, cracks, small losses should be classied as caused

by natural erosion of the mortar.

Some of the mortars in the joints between the historical

bricks were complemented with mortars during modern or

contemporary repairs. The state of preservation of these

mortars is varied and depends primarily on their compo-

sition, i.e., the type of binder and its proportions with the

ller. In many places, modern mortars have disintegrated

and washed out on the surface and are in much worse con-

dition than the historical ones.

Brick wall – modern repairs

In some areas, especially in the basement, the layers of

bricks near the surface are saturated with salts or covered

with their crusty layers, and the mortars are disintegrated

and scattered. It was found that in many places the bricks

were laid with mortar with a large amount of cement, and

only the top layer of joints was made of lime/cement-lime

mortar, which was destroyed.

Fig. 7. Castle in Koło.

Examples of the state of

preservation of the medieval face

of the wall

(photo by K. Polak, 2020)

Il. 7. Zamek w Kole.

Przykłady stanu zachowania

średniowiecznego lica muru

(fot. K. Polak, 2020)

Fig. 8. Castle in Koło. Examples

of the state of preservation

of the tower walls

(photo by K. Polak, 2020)

Il. 8. Zamek w Kole.

Przykłady stanu zachowania

murów wieży

(fot. K. Polak, 2020)

Conservation studies of the ruins of the Gothic Kazimierz castle (2

nd

half of the 14

th

century) in Koło (Gozdów) 67

Pavements and covers

During the last renovations, the planes of the crown of

the walls were protected with a covering of bricks laid on

the damaged crown without levelling the layers, which re-

sulted in its plastic shape (Fig. 9). While the contemporary

roong on the crowns is mostly completely preserved, the

pavements have missing bricks in many places, especial-

ly on the edges, where the inside of the wall structure is

exposed. Apart from natural factors, the destruction of the

covers is facilitated by walking on the pavements and the

tops of the walls. The places of climbing are also on the

tromps on the tower. Their bevels were covered with a lay-

er of mortar to protect the surface from water and stabilize

the damaged bricks. Currently, due to cracks and mortar

losses, the covers do not have a protective function. The

formation of cracks, hollows and voids is conducive to the

colonization of these places by vegetation, which is a rea-

son for large numbers of various plant species growing on

pavements, caps and slanted and horizontal places with an

exposed structure.

Noteworthy are mineral layers on the face of the wall

below the planes. They were formed as a result of depo-

sition of mortar components on bricks washed away by

rainwater.

Historical face of the stone wall

The original face of the stone wall is preserved in only

a few fragments. The mortar in the joints usually comes

from later repairs, but the boulders are rmly embedded

and the layer system is claried. The preserved original

mortars are cohesive and compact, but cracks appeared in

many places, and gaps of various widths appeared directly

at the boulders.

The face of the stone wall – repairs

Most of the face of the stone wall (Fig. 10) was clas-

sied as repairs and additions. They are locally covered

with microbial layers and grati. The mortars in the joints

are preserved in various condition, due to various compo-

sition of the mortar and their technique of preparing. The

mortar is washed out in many places. Some of the res-

torations do not meet the basic restoration requirements

due to the accidental selection of the material, careless,

unprofessional surface treatment and incorrect parameters

of the applied mortar.

Sandstone squares set between granite boulders re -

quire special attention. The condition of these elements

is poor. The stone has disintegrated, locally delaminating.

The edges of the blocks are weakened and crumbling. The

surface is covered with unevenly dark layers. The disturb-

ing state of preservation of the sandstone squares results

primarily from the intensive action of the destructive fac-

tors on the porous rock surrounded by materials with dif-

ferent capillary properties: igneous rocks, which are the

main building material of the wall and mortars.

Summary

Conservation research is an essential element of conser-

vation design, especially in this type of architecture with its

transformations and various conditions [16]. Conservation

studies of the ruins of the castle in Koło made it possible

to recognize its construction technique, repairs and state of

preservation, and to assess them from the conservation and

restoration point of view. The ndings from the conserva-

tion and architectural research became the basis for formu-

lating conservation conclusions regarding both the form

of the object and the technological details of the planned

Fig. 9. Castle in Koło.

The crown of the breastwork

softly prepared during renovation

works in the 20

th

century

(photo by K. Witkowska, 2020)

Il. 9. Zamek w Kole.

Korona przedpiersia miękko

opracowana podczas prac

remontowych w XX w.

(fot. K. Witkowska, 2020)

68 Piotr Niemcewicz, Katarzyna Polak, Aleksandra Gralińska-Grubecka et al.

works. It was stated that the walls of the castle should re-

main in a state of ruin with full access to them and leaving

modern conservation interventions as an element of the

building history of the monument. Conservation interven-

tion should be limited to a minimum, mainly where it is

required by the state of preservation, the presence of harm-

ful materials and the need to protect the structure of the

walls. Such places are, among others, pavements, crowns

of walls and planes. Areas that are dicult to implement

and require prudence from the contractor are all shreds

and forging. These places should remain in the form of

a “destroyed wall”, while stabilizing cracks in bricks and

mortars and lling in losses only in those places that may

contribute to further destruction of the wall.

After examining the contemporary mortars used in the

20

th

century, most of them were allowed to remain in the

building

10

. It was found that despite the content of cement

binders, physical and mechanical parameters do not pro-

vide a risk to historical materials.

Very good, despite the passage of years, state of pres-

ervation of historical mortars, high mechanical strength

conrmed during in situ and laboratory tests, excellent

adhesion, very good capillary properties and the hydraulic

nature of the binder prompt further research into the tech-

nology of the medieval masonry mortars. The analysis of

the castle in Koło from two perspectives – architectural

and construction design as well as conservation research

gives the opportunity to comprehensively address the

problem of the preservation of the facility and develop

a valuable, comprehensive project based on the interdis-

ciplinary knowledge and experience of the specjalists in

various elds.

Translated by

Marta Chylińska

10

Recommendations included in the architectural research docu-

mentation (M. Prarat and U. Schaaf).

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ceglanego i kamiennego oraz

nawarstwienia mikrobiologiczne

(fot. A. Gralińska-Grubecka, 2020)

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Abstract

Conservation studies of the ruins of the Gothic Kazimierz castle (2

nd

half of the 14

th

century) in Koło (Gozdów)

The purpose of this article is to present the conservation research carried out as part of the revitalization project of the ruins of the castle in Koło.

Basis of the recognition of the monument’s construction technique, identication and determination of the properties of historical and contemporary

materials, assessment of the state of preservation and analysis of destructive factors developed a program of conservation works. Research was car-

ried out considering the ndings of architectural research. Laboratory tests of the collected material were carried out by a wide team of employees

using specialized research techniques. Their results are presented in this article and include petrographic, chemical and thermogravimetric analyses

of mortars, rocks and bricks, their capillary and mechanical properties, salinity analysis and microbiological analyses of materials. The undeniable

value of the conducted research is a detailed diagnosis of historical building materials, which is a signicant contribution to the knowledge of old

construction techniques.

Key words: medieval architecture, building materials, material testing, architectural conservation

Streszczenie

Badania konserwatorskie ruin gotyckiego zamku kazimierzowskiego (2. poł. XIV w.) w Kole (Gozdów)

W artykule przedstawiono wyniki badań konserwatorskich zrealizowanych w ramach projektu rewitalizacji ruin zamku w Kole. Obejmowały one

rozpoznanie techniki wykonania zabytku, identykację i określenie właściwości materiałów historycznych i współczesnych, ocenę stanu zachowania,

analizę czynników niszczących, które wraz z wynikami badań architektonicznych stanowiły podstawę opracowania programu prac konserwatorskich

obiektu. Analizę zgromadzonego materiału realizował szeroki zespół z wykorzystaniem specjalistycznych technik badawczych. Wyniki przedstawio-

ne w artykule obejmują petrograę, analizę chemiczną, termograwimetrię oraz właściwości kapilarne i mechaniczne zapraw, skał i

cegieł, stopień

zasolenia oraz analizy mikrobiologiczne materiałów. Niepodważalną wartością przeprowadzonych badań, stanowiącą znaczący wkład w zasób wie-

dzy, jest szczegółowe rozpoznanie historycznych materiałów oraz zastosowanych technik budowlanych.

Słowa kluczowe: architektura średniowieczna, materiały budowlane, badania materiałów, konserwacja architektury