Kinds of damages and conservation and restoration methods in restoration of works of art on the transparent paper

Arhitektonski crteži na paus papiru javili su se u 19. stoljeću. Prvi kemijski tretirani papiri proizvedeni su u Francuskoj 1846., a proces je komercijalno razvila tvrtka Warren de la Rue u Londonu. Paus papir odlikuje velika prozirnost i propusnost svjetlosti što je postignuto impregnacijom papirne pulpe uljima i smolama te dodatnim izlaganjem zraku te sušenjem navedene tvari stvaraju proziran papir. Tipična sredstva za postizanje prozirnosti jesu: kanadski balzam (tekuća smola koja se dobiva iz smole jele), dammar i laneno ulje. U dvadesetom stoljeću se karakteristična prozirnost paus papira dodatno unapređujete je osmišljen kako bi se mogle izvoditi kopije te crteži i nacrti za arhitektonske i projektantske potrebe. Uz prozirnost, jedna od glavnih karakteristika prozirnog papira jest jaka osjetljivost i reakcija u doticaju s vlagom. Sitni fibrili su u postupku proizvodnje usitnjavani u ogromnim količinama vode pa su vlakna jako nabubrena. Kada se papir osuši, vlakna “pamte”, pa u ponovnom kontaktu s vodom jako nabubre. Vlakna prozirnog papira se šire u širinu 10-20 posto, a gotovo ništa ili vrlo malo u dužinu. Vlakna prozirnog papira koji je samo impregniran, nemaju toliko izraženu higroekspanzivnost, nego ta impregnacija štiti papir od utjecaja vlage. Stoga, ovisno o kvaliteti papira, njegovoj vrsti, ali i količini oštećenja, bira se zadovoljavajuća metoda pri konzerviranju i restauriranju navedenog papira. Najčešće se pristupa samo djelomičnom popravljanju poderotina te izražajnijih pregiba. Podljepljivanje treba pokušati izbjeći jer se njime mijenja karakter objekta i zadire u strukturu papira.Earliest examples of architectural drawings on tracing paper are dating from the 19th century. First chemically treated papers were produced in France in 1846., the production process was further commercially developed by the firm Warren de la Rue in London. The transparency of the paper and light penetration is achieved by impregnation of the pulp with oils and resins, with additional exposure to air and drying these substances create a translucent paper. The typical agents used for achieving transparency are; Canada balsam, (liquid resin that is obtained from the resin of fir tree), dammar and linseed oil. The characteristic transparency of tracing paper was further improved in the twentieth century, since it was invented for the purpose of deriving copies and drawings and designs for architectural and engineering needs. With transparency one of the main characteristics of transparent paper is strong sensitivity and reaction in contact with moisture. In the process of production small fibrils are milled in huge amounts of water, so the fibers are very swollen. When the paper dries, the fibers “remember”, so in the anewed contact with water they became very swollen again. Transparent paper fibers are spread in width from 10 to 20 % , and almost nothing or very little in length. Fibers of transparent paper that is only impregnated, don’t behave so much hygroexpansive, yet the impregnation protects the paper from moisture hygroexpansive. For this reason, depending on the quality of the paper, its sort and the amount of damage, a adequate method is chosen to carry out conservation of the mentioned paper. Most often, treatments are performed only as partial consolidation of tears and intense foldings. Lining should be avoided because it may cause changes in the character of the object and it penetrates into the structure of paper

EFFECT OF LIGHT ON THE AGING, CORROSION, AND DEGRADATION OF MATERIALS, IN RELATION TO THE ENHANCED REMOVAL OF ORGANIC POLLUTANTS

A review on advanced photochemical processes influencing properties of materials is presented. Particular emphasis is given on photolytic processes for the removal of pollutants. Separately are presented methods for the removal of biological pollution. Major concern is paid to the methods for removal of persistent chemical pollutants. Two major groups of processes are known: homogenous and heterogeneous photocatalytic methods. The heterogeneous photocatalysis is usually done with semiconductor nanoparticles, capable to absorb light. In semiconductor the absorption of light quanta is connected with the promotion of electron(s) from valence to conduction band, leaving a positively charged hole(s) in CB. Electrons and holes can react with adsorbed molecules including water molecules. In this way the reactive intermediates are produced, which upon the sequence of reactions end with complete mineralization of ingredients. The scaling-up of heterogeneous photocatalytic process is closely connected with efficacy of them. As a matter of fact, many factors are involved in kinetics of photocatalysis: concentration of pollutants; concentration of catalyst; temperature; radiant flux; quantum yield; dopants; etc. The interrelations among various parameters are mostly nonlinear, and construction of the photoreactor is very demanding task. In last 30 years a lot of study was done, and general conclusion is that TiO2 (mostly anatase) is most efficient photocatalyst, but there is a lot of work needed on improvement of such processes

PHOTOCHEMICAL ACTIVATION OF AIR POLLUTANTS, RELATED TO THE PRESERVATION OF CULTURAL HERITAGE

It is well known that the exposition to air and weather markedly enhances derogation of all artifacts. In this report, the contribution of light (particularly sunlight) to marked speed-up of the oxidation and other changes by exposition to atmosphere will be analyzed. Five major mechanisms of the effect of insolation can be identified: 1. First is a trivial one – the heating effect which enhances all chemical processes. 2. Photoexcitation of material from which the item is made, turning it more reactive toward air oxygen (and to other present substances). 3. Sensitization of oxygen by excitation to singlet state in which it is extremely reactive, and can react even with inert materials. 4. Photochemical transformation of volatile organic compounds (VOC), primarily aldehydes and ketones, that can with oxygen yield organic acids and hydroperoxides which definitely harm majority of materials. 5. In contact of oxygen and another material, upon the absorption of light quanta, a charge transfer process can occur, giving yield to pairs of ion-radicals, which further can be transformed in various reactive product

EFFECT OF LIGHT ON THE AGING, CORROSION, AND DEGRADATION OF MATERIALS, IN RELATION TO THE ENHANCED REMOVAL OF ORGANIC POLLUTANTS

A review on advanced photochemical processes influencing properties of materials is presented. Particular emphasis is given on photolytic processes for the removal of pollutants. Separately are presented methods for the removal of biological pollution. Major concern is paid to the methods for removal of persistent chemical pollutants. Two major groups of processes are known: homogenous and heterogeneous photocatalytic methods. The heterogeneous photocatalysis is usually done with semiconductor nanoparticles, capable to absorb light. In semiconductor the absorption of light quanta is connected with the promotion of electron(s) from valence to conduction band, leaving a positively charged hole(s) in CB. Electrons and holes can react with adsorbed molecules including water molecules. In this way the reactive intermediates are produced, which upon the sequence of reactions end with complete mineralization of ingredients. The scaling-up of heterogeneous photocatalytic process is closely connected with efficacy of them. As a matter of fact, many factors are involved in kinetics of photocatalysis: concentration of pollutants; concentration of catalyst; temperature; radiant flux; quantum yield; dopants; etc. The interrelations among various parameters are mostly nonlinear, and construction of the photoreactor is very demanding task. In last 30 years a lot of study was done, and general conclusion is that TiO2 (mostly anatase) is most efficient photocatalyst, but there is a lot of work needed on improvement of such processes

Simple Method for the Estimation of pKa of Amines

A simple and efficient model for the estimation of alkylamine basicities (through corresponding pKa values) is developed. Model uses partial atomic charges of hydrogen and of neighboring nitrogen cal-culated by MNDO-PM6 semiempirical model, taking into account the order of the substitution on nitrogen

ANALIZA I PROCJENA RIZIKA ZA RADNO MJESTO VOZAČA PRI OBAVLJANJU ŠUMSKIH RADOVA

Tema završnog rada je Analiza i procjena rizika za radno mjesto vozača pri obavljanju šumskih radova. U procesu pridobivanja drveta, nakon siječe i izrade slijedi faza privlačenja i prijevoza drveta. Privlačenje je premještanje stabla od panja do pomoćnog stovarišta. Privlačenje drva obavlja se šumskim zglobnim traktorom uz pomoć vitla, po izrađenim šumskim putevima. Ovaj posao može raditi jedan radnik odnosno traktorist koji sam kopča drvo ili ima pomoćnika koji obavlja kopčanje

Kinds of damages and conservation and restoration methods in restoration of works of art on the transparent paper

Arhitektonski crteži na paus papiru javili su se u 19. stoljeću. Prvi kemijski tretirani papiri proizvedeni su u Francuskoj 1846., a proces je komercijalno razvila tvrtka Warren de la Rue u Londonu. Paus papir odlikuje velika prozirnost i propusnost svjetlosti što je postignuto impregnacijom papirne pulpe uljima i smolama te dodatnim izlaganjem zraku te sušenjem navedene tvari stvaraju proziran papir. Tipična sredstva za postizanje prozirnosti jesu: kanadski balzam (tekuća smola koja se dobiva iz smole jele), dammar i laneno ulje. U dvadesetom stoljeću se karakteristična prozirnost paus papira dodatno unapređujete je osmišljen kako bi se mogle izvoditi kopije te crteži i nacrti za arhitektonske i projektantske potrebe. Uz prozirnost, jedna od glavnih karakteristika prozirnog papira jest jaka osjetljivost i reakcija u doticaju s vlagom. Sitni fibrili su u postupku proizvodnje usitnjavani u ogromnim količinama vode pa su vlakna jako nabubrena. Kada se papir osuši, vlakna “pamte”, pa u ponovnom kontaktu s vodom jako nabubre. Vlakna prozirnog papira se šire u širinu 10-20 posto, a gotovo ništa ili vrlo malo u dužinu. Vlakna prozirnog papira koji je samo impregniran, nemaju toliko izraženu higroekspanzivnost, nego ta impregnacija štiti papir od utjecaja vlage. Stoga, ovisno o kvaliteti papira, njegovoj vrsti, ali i količini oštećenja, bira se zadovoljavajuća metoda pri konzerviranju i restauriranju navedenog papira. Najčešće se pristupa samo djelomičnom popravljanju poderotina te izražajnijih pregiba. Podljepljivanje treba pokušati izbjeći jer se njime mijenja karakter objekta i zadire u strukturu papira.Earliest examples of architectural drawings on tracing paper are dating from the 19th century. First chemically treated papers were produced in France in 1846., the production process was further commercially developed by the firm Warren de la Rue in London. The transparency of the paper and light penetration is achieved by impregnation of the pulp with oils and resins, with additional exposure to air and drying these substances create a translucent paper. The typical agents used for achieving transparency are; Canada balsam, (liquid resin that is obtained from the resin of fir tree), dammar and linseed oil. The characteristic transparency of tracing paper was further improved in the twentieth century, since it was invented for the purpose of deriving copies and drawings and designs for architectural and engineering needs. With transparency one of the main characteristics of transparent paper is strong sensitivity and reaction in contact with moisture. In the process of production small fibrils are milled in huge amounts of water, so the fibers are very swollen. When the paper dries, the fibers “remember”, so in the anewed contact with water they became very swollen again. Transparent paper fibers are spread in width from 10 to 20 % , and almost nothing or very little in length. Fibers of transparent paper that is only impregnated, don’t behave so much hygroexpansive, yet the impregnation protects the paper from moisture hygroexpansive. For this reason, depending on the quality of the paper, its sort and the amount of damage, a adequate method is chosen to carry out conservation of the mentioned paper. Most often, treatments are performed only as partial consolidation of tears and intense foldings. Lining should be avoided because it may cause changes in the character of the object and it penetrates into the structure of paper

ANALIZA I PROCJENA RIZIKA ZA RADNO MJESTO VOZAČA PRI OBAVLJANJU ŠUMSKIH RADOVA

Tema završnog rada je Analiza i procjena rizika za radno mjesto vozača pri obavljanju šumskih radova. U procesu pridobivanja drveta, nakon siječe i izrade slijedi faza privlačenja i prijevoza drveta. Privlačenje je premještanje stabla od panja do pomoćnog stovarišta. Privlačenje drva obavlja se šumskim zglobnim traktorom uz pomoć vitla, po izrađenim šumskim putevima. Ovaj posao može raditi jedan radnik odnosno traktorist koji sam kopča drvo ili ima pomoćnika koji obavlja kopčanje

Summary: Contribution of the Krk diaspora to the Croatian War of Independence (fall - winter 1991/1992) – memoirs

After the summer of 1991 it was clear that peace was nowhere in sight and that we would have to join in on mass scale the defence of our country. Problems with providing the Krk unit with basic military equipment were turning up already at the very beginning. The day scheduled for the departure of the first group of soldiers from the island was getting closer and they were equipped with uniforms of the Jugoslav People’s Army (JNA), which at that time was the only available thing, but in our oppinion unacceptable. My friends and me were tasked to try to solve the problem. We got in touch with our islanders in New York and other places in the USA. Thanks to the effort of our people in New York we were able to contact a company manufacturing goods for the US Army and buy their products at factory prices. Compared with the prices in Europe, it was five times cheaper. What impressed us the most, is the fact that our people in the USA organized the collection of the necessary money on their own, our job was just to use the catalogue and order the items and quantity needed