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Electron Microscopy Sciences

Technical Data Sheets

JB-4 Plus Embedding Media

EMS #14272-00

JB4 Plus Embedding Kit is a unique polymer embedding material that gives a higher level of morphological detail than Paraffin processed tissues. A water-soluble media, JB-4 does not require dehydration to absolute alcohol except for dense, bloody, or fatty tissue specimens. JB-4 Plus offers all the benefits of our regular JB-4 formulation with the additional advantages of a cooler acting accelerator and the production of clear blocks. A clear polymer embedding matrix is essential to numerous histological and histochemical procedures, most notably in ophthalmic applications. A water-soluble media, JB-4 Plus does not require dehydration to abosolute alcohol except for dense, bloody or fatty tissue specimens. JB-4 is excellent for routine stains, special stains, and histochemical staining. Clearing agents such as xylene and chloroform are not required. The polymerization of JB-4 Plus is exothermic, which is easily controlled by polymerizing on ice or by using refrigeration at 4°C. All JB-4 Plus Type Embedding kits must be used under a chemical fume hood.

Sections of JB-4 Plus embedded material can be cut at 0.5 to 3.0 microns or thicker. Microtones designed for plastic sectioning are required as are glass, Ralph, or tungsten carbide, or for the best result diamond knives. Diatome U.S. has good selection of Diamond Histo-Knives, which are excellent for sectioning JB-4 Plus blocks. Sections can be stained for routine histological or histochemical procedures. Immunohistochemical procedures are not recommended for JB-4 as the glycol methacrylate cannot be removed from the section and may block antigen sites for most antibody reactions. As an alternative we recommend the LR White, Unicryl or Micro-Bed (See EMS catalog for more information)

Note: It is recommended that the Embedding Kit be used under a chemical fume hood with appropriate gloves.


Specimens can be fixed in 10% Neutral Buffered Formalin or other routine histological fixative. We suggest using HISTOCHOICE™ MB® (EMS Cat #16786), a formaldehyde-free fixation. Routine specimen sizes for soft tissue should be no more than 2 x 2 x 2cm with fixation at a minimum of four hours to overnight. Fatty or dense tissues should be fixed overnight. Lager bone specimens, will requires fixation overnight or longer depending on the specimen size. Fixation can be at room temperature or 4°C. Cold fixation will extend the time required for the specimen to be penetrated and fixed. Larger bone specimens will require longer fixation times, dependent on the size and density of the bone. Bone specimens are not decalcified prior to fixation. Note that while JB-4 Plus can be used for bone specimens, polymerized JB-4 Plus is slightly softer that the JB-4 Embedding formulation, therefore JB-4 is recommended for most bone procedures.


Dehydration can be completed at room temperature or 4°C. This process can also be done with a routine tissue processor, stopped at the end of the last alcohol step and removed for infiltration. Please note that polymers cannot be used in routine histology tissue processors, at any time. It may void the warranty and possibly begin to polymerize in the system thereby blocking the lines. Check with the manufacturer prior to attempting infiltration on any unit.


Infiltration Solution Mixing Procedures:

The following amounts of material are used for one 100ml batch of infiltration:

  • JB-4 Plus Solution A (Monomer) 100 ml
  • Benzoyl Peroxide, Plasticized (Catalyst) 1.25 g

Carefully weigh 1.25 g of catalyst (benzoyl peroxide plasticized) and add to 100 ml Solution A while stirring on a magnetic stirrer. Mix until dissolved approximately 10 to 20 minutes. Measurement of the catalyst is critical as it will control the rate of polymerization of the plastic and the exothermic reaction. This infiltration solution can be stored for up to two weeks in a dark cool area or in the refrigerator at 4°C.

Infiltration Procedure:

Infiltration is performed at room temperature or at 4°C. Do not expose the samples to heat or direct light during infiltration. The specimens should be placed in two to three changes of infiltration solution to allow for the removal or replacement of all alcohols or tissue fluids.

The amount of infiltration solution used is approximately 8 to 10 times that of the volume of the specimen. The changes of fluid should be every 10 to 90 minutes for smaller specimens. The time in each change is dependent on the size of the specimen. When infiltration is complete the tissue generally appears translucent and in most cases will sink to the bottom of the container.

Infiltration should be done on a slow rotator, hematology shaker table or inverted several times during the process to allow complete saturation.

Infiltration Solution:

Infiltration Solution Volume JB-4 Plus Benzoyl Solution A Peroxide
100ml 100ml + 1.25ml
50ml 50ml + 0.625ml
25ml 25ml + 0.3125ml


The polymerization process should be under anaerobic conditions with the use of block holders, under light vacuum or in an air-tight container.

Prior to mixing the Embedding Solution collect and prepare the following materials; embedding molds, block holders, labels, gloves, instruments, an ice bath, and the specimens. Do not pre-cool the molds as this may cause condensation and prevent even polymerization of the block face. To prevent polymerization from occurring too fast and possible overheating of the tissue it is recommended that the polymerization process for embedding be slowed by completing it in the refrigerator or in a cold room at 4°C. Note that this may extend the polymerization from several hours to overnight.

Embedding Solution Mixing Procedure:

Make fresh Solution A following the directions in infiltration solution and procedures above. Do not use old or used catalyzed Infiltration Solution for the embedding solutions.

The following amounts of material are used for 25 ml of embedding solution:

  • Infiltration Solution 25.0 ml
  • JB-4 Solution B (Accelerator) 1.0 ml (must be an exact measurement)

Embedding Solution:

Embedding Solution Volume Fresh Infiltration JB-4Plus Solution B
50ml 50ml + 2 ml
25ml 25ml + 1ml


Mix 25 ml of fresh made Infiltration Solution and 1.0 ml of JB-4 Plus Solution B thoroughly and begin embedding immediately. Drain excess Infiltration Solution off the specimen before orienting in the block holder. The block holder is essential to exclude oxygen during the polymerization process. If Block holders are not used, cover the molds with an air tight film or place under vacuum at no more that 15psi, preferably in a cold room at 4°C or a refrigerator. Beem capsules may be capped for embedding

The blocks will be clear to very pale yellow. This color shift is not a problem and will not effect the block hardness. The top of the block may have a liquid film on it and can be removed by draining or drying the block in a desiccator for several hours to overnight.

Deplasticizing and Staining:

JB-4 Plus is a glycol methacrylate based polymer and it cannot be removed completely from sections, therefore no organic solvents are required. Routine histology stains and most histochemistry can be run on the sections. High molecular weight special stains or immunohistochemical reactions may not penetrate the polymerized plastic in the sections and may result in an incomplete reaction.


May be harmful if swallowed. Use under a fume hood with appropriate gloves. Components may cause irritation and or allergic skin reaction. Avoid contact with eyes, skin and clothing. Avoid inhalation of the vapors. Wash hands or expose areas thoroughly after handling the solutions.


Do not heat over an open flame. Avoid electrical or static sparks. Store un-catalysed resin in the original containers at room temperature in a dark cool area.

First Aid:

In case of contact with any component or mixed solution, immediately flush area with plenty of water for at least 15 minutes. Should either unpolymerized or polymerized material contact the eyes flush with water

Water for at least 15 minutes. Should either unpolymerized or polymerized material contact the eyes flush with water ofr at least 15 minutes. If swallowed, drink water to excess and call a physician immediately. Never give anything by mouth to someone who is unconscious.


Refrigeration of the kit components is not required but they do required storage in a cool dark place. Do not store in the light or in a heated area as it may cause the monomer to polymerize. The catalyst, plasticized benzoyl peroxide, is organic peroxide that is shipped dry and does not required special storage. Please note that the catalyst is formulated to remain stable and weigh correctly for this procedure without any adjustments to the amounts recommended. The catalyst should be kept tightly sealed. The catalyst may decompose with age, therefore we recommend carefully monitoring the date received and using the catalyst only with the kit it came in for best results.

Catalyst Disposal Procedure:

The catalyst can be destroyed by slowly adding and mixing it in small portions of the catalyst at 4 times or more the volume to weight of 10% sodium hydroxide solution in water. Do not allow material to settle in lumps or stand in layers and mix until dissolved completely. Dispose of this solution, Monomer A, and the accelerator with other hazardous wastes in accordance with local, state, and federal regulations.

Online Ordering

14270-00 JB-4 Plus Embedding Kit
14270-01 JB-4 Plus Solution A
14270-04 JB-4 Plus Solution B
14270-06 JB-4 Plus Catalyst
15740-01 Formalin Neutral Buffered
70175-50 Plastic Block Holder
70176 Molding Cup Tray
70180 Peel-Away Molds