Background on SPI-Pon 812 Resin:

SPI-Pon 812 was developed as a direct substitute for the epoxy resin known as  "EPON® 812". At the time of its discontinuation by Shell Chemical, it was the most widely used embedding resin in the world for use in preparing samples for electron microscopy. It has been proven that there are no differences between SPI-PON 812 and EPON 812 with regards to sectioning, staining, or stability in the electron beam.

SPI-Pon 812 is the preferred resin for samples that have solubilities to resin monomers (that is, the samples can potentially  be dissolved by the  monomer or combination of monomers). Special methods have been published for applications with these kinds of samples. SPI-Pon 812  resin has great versatility. It can be the embedding resin of choice for biological tissue material as well as materials such as catalysts or plastic samples. No other resin can be used over such a broad range of samples representing such a wide range of hardness.

Most users of the SPI-Pon resin kit cure their samples at 60°C. Faster cures are possible at slightly higher temperatures, up to 70°C. SPI-Pon 812 in the cured state is completely inert with regards to osmium tetroxide exposure and is the preferred resin for those staining with osmium tetroxide. This is the case for both life science and materials science samples.

Note about bubbles in the final cured block:

A common "problem" with resin monomer embedding materials is the presence of bubbles in the final cured block. This is usually the result of retained moisture in the sample. Another source of bubbles is mixing of the components  too vigorously. Depending on the sample itself, there are different ways one can use to remove residual moisture. We have found that no  matter the source, pumping on the mixed ingredients for a short time with a mechanical pump vacuum will cause the bubbles to rise and exist the system. The precise amount of time this takes will be determined by how fast the system polymerizes.

Hardness vs. viscosity:

Another one of the tradeoffs faced regularly by microscopists is that of resin viscosity vs. hardness of the final block. By way of the addition of excess hardener, one can make a block out of SPI-Pon 812 that is as hard as any resin and certainly harder than a lot of resins. Polymerizing under such conditions does result in a higher viscosity of the resin and therefore potentially less effective infiltration. But we always recommend this as the place to start since the alternatives are both more expensive and more complicated to use. For a lower viscosity embedment, we recommend trying SPI-Chem Low Acid GMA,TEM formulation. The GMA monomer has a viscosity slightly less than that of water.

Particle "pull-out":

When embedding hard spherical particles, sometimes the particles themselves are being pulled out by the action of the knife, so that the sections exhibit just the "ghosts" or holes where the particles once were. In order to reduce the tendency for this to happened, we recommend the use of SPI-Chem? (3-glycidoxypropyl) trimethoxysilane.

An understated potential safety risk:

We are addressing now the cured block, something that to most people is about as inert of a material as one will find. A standard practice in many laboratories is to use a small jeweler's or  small hack saw to cut the block down to the right size and shape. We want to address the potential dust that is generated and how its exposure by inhalation should be minimized.