FAQ

A- What can cause bubbles in the opaque after firing?
1) Metal contamination: Check alloy manufacturer’s recommended spruing and finishing of porcelain bearing surfaces. Sandblasting with 110 – 125 micron aluminous oxide (Blastite 2) is recommended (30-35 psi).

2) Paste Opaque applied too thick: Paste opaque tends to puddle in margin, shoulder, and occlusal areas when applied too thick. Hence, preventing these areas from drying properly. It is recommended to apply two thin coats of opaque rather than one thick coat to mask the metal. Prolonging the drying time may also help.

3) Failure to use Pre-Opaque: HeraCeram Pre-Opaque enhances the conditioning of the porcelain bearing alloy surface. It can help remedy bubbling occurrences that originate from the alloy surface. Refer to HeraCeram firing program chart for instructions on proper use of Pre-Opaque.

4) Opaque fired too low: Fired opaque must exhibit a high luster (shinier than conventional opaque). If necessary, raise the opaque firing temperature until this appearance is achieved.

5) Check opaque drying temperature and drying time: Do not place the object under the porcelain furnace muffle until the furnace reaches the low firing temperature as prescribed on the HeraCeram firing program chart. If the temperature is too high, the opaque will begin to boil, and you will notice smoky fumes rising from the opaqued surface. The resulting bubbles will remain on the opaque surface, and appear after firing.

B- Why would steam tears appear on the occlusal surface, and interproximally on multi-unit bridges?
1) This may occur if the porcelain starts firing when it is too moist. Be sure not to build up too wet, and allow proper drying time (according to firing chart) before firing. Also, be certain that the vacuum starts at 1112°F (600°C).

C- Why do shades appear too light?
1) Check firing temperatures of 1st body build-up: To achieve accurate shades, and proper translucency that HeraCeram offers, IT IS ESSENTIAL that you achieve an high glossy (almost over fired) appearance, yet without distorting your detailed contours at the first bake. The fine particles of HeraCeram must be properly matured during the first body bake firing. If you do not achieve this appearance during the first fire, it cannot be remedied in subsequent firings.

2) Exercise caution when using opalescent incisals: Do not be too aggressive when utilizing these powders.

3) You may have a vacuum problem: Be sure your vacuum is pulling enough vacuum (28 – 29 inches or 71 – 74 cmHg). Also check furnace and/or connections for any vaccum leaks. Be certain vacuum starts at designated temperature, verifying that vacuum does not start too late during the firing cycle, or porosity may develop.

4) Wrong Modeling liquid: Other manufacturers modeling liquid is not recommended, as it may not be compatible with HeraCeram porcelain. Use HeraCeram modeling liquid or distilled water only.

5) Use Value porcelain sparingly: The Value materials are used to control the brightness of the build-up. If used too aggressively, the final shade may appear lighter than desired.

D- Why are my contours rounded and distorted?
Lower your firing temperatures by 10°-15° F (5° - 7° C) increments while maintaining prescribed hold times.

E- I try to achieve a natural glaze, but it still appears too low.
1) Your firing temperatures may be too low: Under fired porcelain will not glaze properly.

2) Adjust your glaze temperature and/or hold time to achieve desired appearance: High temperature hold time should be no longer than 45 seconds.

F- My artificial glaze is too low.
1) See E- 1 & 2.

2) Mixture of glaze powder and stain liquid is too thin.

3) Do not use other manufacturer’s glaze powder or medium: Glaze powders and mediums, other than HeraCeram’s, will not absorb and seal the porcelain surface properly resulting in an insufficient glaze.

G- I notice checks and cracks after firing.
1) Alloy selection must be within the compatible CTE range accepted by HeraCeram Porcelain. C.T.E. 13.8 – 15.2 @ 600° C C.T.E. 13.5 – 14.9 @ 500° C

2) Utilize the HeraCeram Pre-Opaque.

3) Proper metal substructure support must be achieved: Frameworks must be designed to allow no more than 2.0mm room for porcelain.

4) Metal framework must be designed with rounded corners: Sharp corners, or edges cause stress on ANY porcelain when fired, resulting in checks and cracks in the fired porcelain.

5) Sandblast porcelain-bearing surfaces with 110 – 125 micron aluminous oxide with 30-35 lbs of air pressure.

6) Do not mix other manufacturer’s porcelain, and/or opaque with HeraCeram, for the resulting properties are unknown.

7) You may wish to introduce a slower cooling time: Normally, a slow cool is not required when using HeraCeram. However, depending on the metal to porcelain volume (large bridges, implants) a slower cool of 3-5 minutes may help metal framework, and porcelain to cool at a similar rate in such cases.