department for preventive conservation national ... - WebSajtovi

spreči isticanje smole. Na mestu gde kalup propušta ulivenusmolu dopuna će imati manju čvrstoću (dopuna ćebiti poput gume) i teško ćemo je obraditi (brusiti). Ismolu koja je iscurila iz kalupa teško je očistiti, posebnoiz unutrašnjosti predmeta zatvorenijeg oblika.- kada nismo uspeli kalup da pričvrstimo uz staklona tački dodira stakla i dopune nastaje mala stepenica ina taj način smola može da se slije preko originala (skica1). Može se desiti da deo koji je izliven ima veću tvrdoćuod stakla. Prilikom odstanjivanja takvih nepravilnostimože se desiti da staklo oštetimo, a ponekad i slomimo.- silikonska guma ili bilo koji drugi materijal kojiupotrebljavamo za pričvršćivanje kalupa na staklo nesme da procuri u unutrašnjost kalupa. Ako lepak procuri,na tom delu bi nastala rupica ili u najboljem slučajuudubljenje.Razmak izmeu unutrašnjeg i spoljašnjeg kalupaKada se susrećemo sa većim delovima koji nedostajuili sa vrlo tankim staklom teško je oba kalupa namestititako da se postigne jednaka i pravilna udaljenostunutrašnjeg i spoljašnjeg kalupa, s obzirom na oblikstaklenog predmeta. Ako su kalupi suviše blizu jedandrugome postojala bi mogućnost, da zid bude previšetanak ili čak da se pojavi rupa. Posledice prevelikog razmakaizmeđu kalupa prouzrokuju nastanak predebeledopune (skica 2).Injektovanje i ulivanje smoleU toj fazi je potrebno sasvim precizno namestiti obalevka za ulivanje i izlazak vazduha. Kada injektujemosmolu moramo iglom da uđemo u sam kutak kalupa.Levkovi moraju da stoje tako da iz njih smola ne možeda procuri, a ujedno moraju biti postavljeni tačno u uglukalupa, tako da iz kalupa može da izađe sav vazduh (slika1). Rad sa levkovima je veoma dugotrajan. Kod malihdopuna ponekad se desi da nema prostora za montažulevka. Kad odstranimo kalup na mestu gde su bili levkoviostane štrčeći deo, koji moramo da odrežemo i izbrusimodo istog istog sjaja kakav ima okolna površina.Kada unosimo epoksi smolu putem injekcije, bitno je daiglom prodremo samo kroz spoljašnji kalup i to tačno ukutak prostora koji dopunjavamo, inače postoji mogućnostda u kutku ostane mehurić. Kao što smo pre istakli,kalup je nežno prilepljen na staklo. Ako ga previše pritiskamoili vučemo popustiće mesto gde je kalup zalepljeni tu će smola curiti. Pri prodoru igle ne smemo dapotisnemo unutrašni kalup, pogotovo u fazi kada ubriz-- The mould should be fixed to glass in such a way asto prevent resin from flowing out. In places where themould is leaking, the cast will be softer (as made of rubber)and thus more difficult to treat (cut). The cleaningof resin will also be difficult, particularly from the insideof a glass object having a specific form.- If we fail to fix the mould close to the wall, a stepmay form where the original glass and the cast come together,and resin may flow over the original (Scheme 1)forming an extended piece. Such a piece may be moresolid than glass itself. When removing it, glass may bedamaged or broken.- If silicone rubber or any other material used to fixthe mould to glass has flowed into the mould, a smallhole or at least a hollow will be formed there.Maintaining the space between inner and outermouldsWhen the area of missing piece is large or the glassis very thin, it is difficult to place both moulds so thatthe distance between them is kept uniform with regardto the shape of the glass object. If the moulds are placedtoo closely, the resin cast will be too thin or have holesin it. If the moulds are placed too far away from each other,the cast will be too thick (Scheme 2).Injecting and casting resinIn order to introduce resin into a mould, it can beinjected through a hole in the mould or cast in by meansof a funnel, which should be placed precisely, or, if resinis injected, a needle should be pushed in the right place.The funnels should be placed in the highest part of themould so that resin does not flow out, and precisely inthe corner of the mould so that the air may flow outfrom the mould (Fig. 1). The work with funnels takes upa good deal of time and if the cast is small, there is evennot enough space to place the funnels. After the mouldhas been removed, the protruding part remains in theform of a funnel; this part should be cut off and polishedto obtain the same gloss as the surrounding surface.When epoxy resin is injected, it is of key importance topush the needle only through the outer mould and preciselytowards the corner of the space being completed,otherwise an air bubble may remain in the corner. As Ihave already mentioned before, the mould is only slightlyglued to glass. If we press or pull it too much, theconnection will relax and the resin will flow out (we areback to the problem of fixing the mould). The inner mouldshould not be pushed away with the needle, particularlywhen epoxy resin is squeezed out of the injection,as all sort of different forces are released then (change inthe needle’s angle; pressing, pulling of the mould). Whenthe mould is filled up with epoxy resin, air may be trappedin the cast’s complex configuration, forming smallholes in the cast, which must be filled up.Air Bubbles and Shrinking of ResinAir bubbles can form within the resin as a mould is fil-155