How to hot mount

Preliminaries to Mounting

Clean the Specimen
The specimen should be cleaned before mounting in order to improve adhesion to the mounting medium. Use acetone or at least alcohol. Cleaning in an ultrasonic bath could be necessary. Remember to dry the specimen well. Clean specimens should be handled with either gloves or tweezers.
Adjust the specimen size to the cylinder size (~ 3.0-5.0 mm distance to cylinder wall).
Adjust the specimen height – the final height of the mount should be approx. 20 mm.
Select the most suitable hot-mounting resin.

How to
Troubleshooting
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Hot-mounting process

Hot mounting - process clips

Small, thin specimens can be supported during the hot mounting process by the use of metal fixation clips.

Hot mounting - process cylinder

The clean and dry specimen is placed in a mounting cylinder in a hot mounting press, and the appropriate mounting resin is added. A temperature of around 180° C and a force of about 250 bar is applied during the embedding of the specimen. Water cooling is used to obtain the shortest possible mounting time.

Two types of hot-mounting resin:

Thermosetting resins

Thermosetting resins cure at elevated temperatures. To avoid porous, non-uniform mounts, it is important that the pressure is always constant and at the right level. Once the mount is cured, the only way to remove the specimen is to destroy the mount.

Thermoplastic resins

Thermoplastic resins soften or melt at elevated temperatures and harden during cooling. This resin type can be used to mount pressure-sensitive specimens. The mounting medium is first heated and then exposed to force when it is soft. This ensures that the mounting medium is pressed into open pores and cracks.

Thermoplastic mounting media can be melted again.

New non-hazardous hot mounting resin PuriFast gives you and your employees a healthier environment to work in. PuriFast is very easy to use during filling and handling to facilitate quick mounting. Read more >

Preheating

In the case of porous and/or pressure-sensitive specimens, such as minerals or electronic parts, it can be a good idea to soften the resin by heating before applying pressure. Preheating is also useful when applying thermoplastic resins.

Using Sensitive Mode, the total heating time is split into two – preheating and heating – where force is applied only during the heating phase and not during the preheating phase.

Temperature Sensitive Specimens

The temperature for the mounting process can be reduced to a minimum of 150° C for all resins. This is useful when dealing with temperature-sensitive materials. If the temperature is reduced, the recommended heating time should be increased accordingly.

Chamfered Ram

A mounted specimen may have sharp edges that can cut up preparation surfaces. This is countered by using a lower ram with chamfered edges. The chamfered lower ram also eliminates the risk of hard samples damaging the mounting unit cylinder.

Selection of Resin / Selection Guide

The choice of resin/mounting media is very important in order to obtain the required result and fulfill the mounting requirements.

The purpose of this guide is to provide detailed information, hints and tricks about the various hot mounting materials. Go to Hot Mounting Selection Guide

	Special applications				Edge retention / general usage
Resin name	ClaroFast	CitoFast	ConduFast	PolyFast	DuroFast	LevoFast	PuriFast	MultiFast
Application	Transparence Crystal clear mounts good for specimens with pores, voids or empty spaces. Can be used in a mixed mount as an insulator for electrolytical preparation or as a backfill for labelling.	Fast Fastest hot mounting resin on the market. Best suited for soft materials or as "backing" for other resins when speed is of essence.	Conductive Conductive resin relevant when electrolytical polishing and etching is used.	SEM analysis Carbon filler enables SEM examination & offers very low shrinkage + high removal rate.	Edge retention Superior edge-retention for hard & medium hard materials with very low risk of gaps.	Edge retention Excellent edge-retention for medium hard & soft materials with very low risk of gaps.	Dust-free No health hazards & dust free. Recommended for soft to medium hard materials.	Routine Bakelite type resin for routine examination of soft to medium hard materials, or as backfill. Three colors available.
Shrinkage level	Low	Low	Low	Very low	Very low	Very low	Medium	Medium
Edge retention	Fair	Fair	Fair	Good	Excellent	Excellent	Fair	Good
Removal rate	High	High	High	High	Low	High	High	Medium
Mount hardness	81 Shore D	86 Shore D	76 Shore D	87 Shore D	86 Shore D	88 Shore D	62 Shore D	87 Shore D
Mounting time* (incl. heat-up)	10.5 min	3.5 min	5 min	5 min	5.5 min	5.5 min	5 min	5 min

Troubleshooting - hot mounting

Problem

Radial Cracking

Cause:
Insufficient distance between specimen edge/corner and cylinder wall, or specimen has sharp corners.
Solution:
Increase cylinder diameter or reduce specimen size. The distance between the specimen and the cylinder wall must be a minimum of 3 mm to avoid cracks in the resin. This is especially critical for specimens with sharp corners.

Shrinkage

Cause:
Incorrect choice of resin.
Solution:
Re-mount a new specimen using a resin with a lower linear shrinkage value.

Blistering

Cause:
Insufficient heating time.
Solution:
Increase heating time, or increase process temperature.

Cause:
Over-cured surface.
Solution:
Decrease process temperature.

Cause:
Entrapped gas within mount.
Solution:
Preheat resin.

Bulging

Cause:
Insufficient cooling.
Solution:
Increase cooling time.

Porosity

Cause:
Excessive temperature.
Solution:
Reduce process temperature.

Voiding within Large Mounts

Cause:
Insufficient heating time.
Solution:
Increase heating time.

Cause:
Excessive temperature.
Solution:
Reduce process temperature.

Cause:
Insufficient force/pressure.
Solution:
Increase mounting force/pressure.

Dull Surface Finish

Cause:
Insufficient heating time.
Solution:
Increase heating time.

Adhesion between Mount and Rams

Cause:
Insufficient application of mould release agent.
Solution:
Apply mould release agent. This must always be applied to the mounting rams as a thin layer before the mounting process begins. This prevents the resins from sticking to the rams and makes it easier to remove the mounts afterwards.

Cause:
Insufficient heating time.
Solution:
Increase heating time.

Cause:
Insufficient force/pressure.
Solution:
Increase mounting force/pressure.

Individual Grains Visible on Mount*

Cause:
Resin has cured without force/pressure.
Solution:
Increase force/pressure during heating cycle.

Cause:
Insufficient heating time.
Solution:
Increase the heating time and/or temperature.

*Thermosetting resins only

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