Lastek 31 C

Silver brazing flux

Lastek 31C is a flux in powder for silver brazing ferrous and non-ferrous alloys.

The flux is active over a broad temperature range and can be used with most of the Lastek silver brazing alloys.

Effective temperature range: 480 – 800 °C.

Specifications & Usage


The flux can be used as a powder or as a paste.

A paste can be made by mixing the powder with distilled or de-ionized water.

Powder fluxes may become clumpy under influence of humidity. Therefore containers have to be kept closed. During use, do not leave the container open for a long time; close them as soon as possible. Always stock containers frost free and do not expose to temperatures above 50 °C (122 °F).


Apply flux on the joint. Dip the heated brazing rod in the flux. The flux will stick to the surface of the rod. Preheat with neutral or reducing flame. As soon as the flux melts and becomes transparent, melt a bit of the silver alloy and spread it along the joint with the flame.

Silver brazing flux residues will be corrosive and need to be removed.

Do not braze or work with fluxes without sufficient ventilation and fume extraction. Do not breathe brazing fumes and gases. Avoid contact with eyes and skin, especially injured skin. In case of contact with eyes or skin rinse immediately with plenty of pure water.


Welding proces: Flux
Material Type: Silver solder
Welding positions: NA
Norm : EN 1045
Classification: FH 10
Norm: DIN 8511
Classification: F-SH1
Minimum packing: 0.25 or 0.5 kg in a plastic container