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Monday, April 29, 2013

Curing polymer clay in a gas oven without thermometer/ Cum sa coci lutul polimeric in cuptorul cu gaz fara termometru

Because not all of you out there have an electric oven and can't really check the temperature in a gas oven without a thermometer, there are some tips that will probably help you. Also, you can't miss out on experimenting with this great medium just because you don't have an electric oven and you might also miss out on some skill development until you get one. Since I've been working with polymer, I've had some accidents regarding its curing temperature and I've learned a few things I want to share with you.

I've lived in various places and many times I didn't have the utensils necessary to craft with me (you can’t really carry everything around with you all the time) and I had to improvise. Since I've used many types of ovens for baking clay, there are some tips that apply to all.

1 - Always preheat the oven, it depends a lot on the gas pressure but usually you have to preheat it for about 10 minutes on minimum.

2 - After preheating the oven put your sculptures, jewelry, etc. inside and make sure that you keep it on the minimum. If you want to be sure that the temperature is over 110/130 degrees Celsius (230/266 F) you can put a bowl of water inside and when it starts boiling you know that the water has reached 100 degrees Celsius and you can put in your things. Remember to keep it on minimum.

3. I usually bake things for 15 minutes if it's a new type of oven I'm not familiar with, and inspect them closely afterwards to see if they are burned or cracked. Make sure that you do that. Afterwards you can bake them a bit longer until you are satisfied with the result with lower or higher temperature.

4. Place a bit of polymer clay with the items you bake and you can cut it or stick something in it to see whether is done or not. This way you won't risk cutting the good pieces.

5.You can also microwave your clay, but I never tried it. However, you can check out this page here where a few tests have been done.

6. Remember that some clays will change colors during baking, so you need to make a test with a few pieces of clay if the project you are making needs exact colors.

7. You have to keep in mind that polymer clay, when it’s just out of the oven, will still be elastic, so it might appear uncured. If you think it’s cured, you should wait for it to cool down and you can try and bake it again.

8. Polymer clay can be cured multiple times in the oven, even when it’s already cured and hardened; you will need this for some projects so don’t be afraid to do it, nothing will happen if you respect the temperatures and curing time. Speaking of temp and time, you should also keep in mind that some brands of polymer clay have different curing times and different temperatures, you will need this if you are trying to combine them. For example Cernit needs a higher curing temperature than Fimo.

I’ve made some charts that you will certainly find useful (scroll over the Romanian text):

Pentru ca nu toata lumea are un cuptor electric si nu prea poti sa masori temperatura la cuptorul cu gaz fara termometru, voi veni cu cateva sfaturi care sa va ajute in directia asta. De asemenea, nu trebuie sa pierzi experienta cu acest mediu minunat doar pentru ca nu ai cuptor electric si s-ar putea sa pierzi si cateva ore bune de dezvoltare a indemanarii in directia asta. De cand lucrez cu lut polimeric, am avut cateva accidente in timpul coacerii si am invatat cateva lucruri pe care vreau sa vi le transmit si voua.

A trebuit sa ma mut des si de multe ori nu am avut ustensilele necesare sa fac anumite lucruri (nu prea poti sa cari totul cu tine) asa ca a trebuit sa improvizez. Din moment ce am folosit mai multe tipuri de cuptoare pentru a coace lutul, am invatat cateva lucruri care se aplica la absolut toate cuptoarele.

1- Intotdeauna se va incinge cuptorul inainte de coacere; in functie de presiunea gazelor se poate tine mai mult dar in general aproximativ 10 minute este perfect.

2- Dupa ce cuptorul a fost incins, se pun proiectele inauntru si se da pe minim. Daca vreti sa fiti siguri ca temperatura a ajuns la 110 grade Celsius, puteti pune inauntru apa si atunci cand aceasta incepe sa fiarba stiti ca a ajuns sigur la 100 grade.

3- De obicei eu tin pentru 15 minute proiectele daca este un tip de cuptor nefamiliar mie, si dupa aceste 15 minute le scot si le analizez. Veti observa ca daca a fost dar focul prea tare, vor mirosi ciudat si isi vor fi schimbat culoarea. Dupa, le puteti pune pentru inca 5-10 minute in cuptor pana obtineti rezultatul dorit.

4- Pentru a elimina orice risc puneti o bucatica de lut polimeric pe tava de coacere si atunci cand nu sunteti sigur daca s-au polimerizat puteti intepa bucata respectiva. Daca se rupe foarte usor, mai trebuie tinute.

5- Puteti sa folositi si cuptorul cu microunde dar personal nu am incercat niciodata. Puteti gasi mai multe detalii pe aceasta pagina.

6- Tineti minte ca unele tipuri de lut isi pot schimba culoarea cand sunt coapte, asa ca daca aveti un proiect care necesita niste culori exacte, puteti face teste cu bucatele mici de lut inainte.

7- De asemenea, trebuie sa tineti seama de faptul ca lutul polimeric imediat scos din cuptor va fi in continuare elastic asa ca poate parea necopt. Daca credeti ca s-a copt, asteptati sa se raceasca si il mai puteti coace inca o data.

8- Lutul se poate coace de nenumarate ori in cuptor chiar daca s-a intarit, pentru unele proiecte este nevoie de coaceri multiple asa ca sa nu va fie frica sa o faceti, nu se va intampla nimic daca respectati temperaturile si durata. Si daca tot vorbim de temperatura si durata, tineti seama de faptul ca unele firme de lut au timpuri si temperaturi diferite, mai ales atunci cand incercati sa le combinati, de exemplu Cernit trebuie copt la o temperatura mai mare decat Fimo.

Am facut niste grafice utile mai jos: 

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