Printing Guidelines Somos® BioClear

Somos® BioClear

Last updated on 30 January 2020


Somos® BioClear is the material for printing clear guides and models with peace of mind. It is ideal for customized, non-implantable limited body contact (<24hr) medical and dental applications. Somos® BioClear has passed stringent ISO 10993-5 Cytotoxicity, ISO 10993-10 Irritation & Sensitization and USP Class VI testing, after following the validated cleaning procedure.

Download the technical data sheet here.

Technical Data

Optical Properties

Ec C 11.5 mJ/cm² [critical exposure]
Dp 6.50 mils [slope of cure-depth vs. In (E) curve]

Safety Instructions

Avoid injuring yourself or others

Please adhere to the following guidelines:

  • Read and understand the Safety Data Sheet (SDS) before using the material.
  • Avoid contact with eyes, skin & clothing by wearing the following Personal Protective Equipment (PPE):
    • Safety Glasses/Goggles
    • Gloves
    • Laboratory Coat
  • Keep the work area clean.
  • Avoid spreading material on clean surfaces.
  • If material is found on clean areas, it should be cleaned off immediately with a disposable paper towel and isopropanol.
  • Wash hands regularly after handling material.
  • Provide adequate ventilation.
  • Prevent build-up of volatile substances from materials and solvents.
  • Remove dust from clean and finished parts.
  • See the Covestro Safe Handling Guide for UV materials for further safety instructions.
  • Products used in <24hr skin or mucosal membrane contact applications biocompatibility test have been passed after strictly following our guidelines.
  • Do not use Somos® Bioclear on applications >24hr in contact with mucosal membrane without additional biocompatibility testing according to ISO10993-5.
  • Validate your production process safety after any changes have been made for example by performing ISO 10993-5 Cytotoxicity
  • Shelf life of printed products is proven for up to 3 weeks. For longer shelf life, extra testing is advised. 

Preparing Equipment

Operating conditions

We recommend the following room conditions:

  • Ambient temperature of 20oC – 25oC (68oF – 77oF)
  • Humidity of less than 40%
  • Minimize dust, as it can build-up and reduce the performance of the optics on your SLA machine, potentially leading to an increase in scattered UV light. Ultimately, this could increase the viscosity of the material in the vat.
  • Use UV filters for lighting and external windows.
  • Provide adequate ventilation. 
  • Keep the work area clean.

Replacing Material

When replacing material, make sure you clean the vat thoroughly, dispose of used material and cleaning products (solvents, paper towels, etc.) properly and follow vat installation procedures.

Machine Replacement

Contact your equipment supplier for up-to-date technical support for your equipment. Below are a few common checks that will help you build parts successfully.

Recoater Blade

  • Keep the re-coater blade clean. Remove debris from the bottom and periodically check the gap and rake of the blade
  • Periodically check the rim level
  • Keep bearing rails clean and oiled
  • Periodically check belts, sprockets and bearings

Optics and Overhead Mirror

  • Keep mirrors and optics dust free and clean. Periodic preventative maintenance will increase the life of the laser beam and improve its quality.
  • Have the laser tuned and serviced periodically. The typical tuning frequency is two to three times a year. This reduces the risk of burn spots on the laser crystals.

Machine Computer

  • Inspect the cooling fans for electronic components regularly to ensure they are working properly.
  • Keep the build tree clean. Having too many build files can corrupt the procycon.mdb, which contains material data, start position and sensor locations.
  • Install back up hard drives to ensure you do not lose any data. This is very important, especially for older equipment.
  • Make sure the latest computer software service packs are installed are your system for optimal performance.
  • Contact your Covestro representative for up to date material parameters in case the parameters are not delivered by your system supplier.
  • When filling the vat, make sure you clean thoroughly, dispose of any old used material. Use cleaning products (solvents, paper towels, etc.) properly and follow vat installation procedures provided by your equipment supplier.
  • Clean any dust of the mirrors and optics.
  • Make sure the laser has been tuned and serviced not more than 4 months ago.
  • Clean the recoater blade.
  • Check machine operating status
    • Periodically check the rim level.
    • Keep bearing rails clean and oiled.
    • Periodically check lead screws.
  • Check & monitor before start of a new build cleanliness & gap distance of the recoater blade
    • Gap distance should be 0.004 inches (0.102 mm)
    • Watch the buildup of the first layers to check if the surface is properly coated with material. Check for signs of material starvation or de-wetting, and adjust appropriately.
  • Set laser scan speed according to your machine & material combination provided by Covestro.
  • Measure & log your material viscosity once a week according to instruction you can find in the instructions. If viscosity value is over 300 Cps above the initial fill value contact your Covestro support engineer.
  • Be aware in medical applications no vat stabilization actions can be performed.

Post Processing

Part-cleaning Procedure – Part 1

  • Drain excess material off the parts in the vat
  • Remove the parts from machine and platform.
  • Rinse the parts for 10 min with 99% isopropanol (IPA) (an automated parts washer, or an ultrasonic cleaner can be used).
  • Brush the parts with isopropanol. This removes the solvent, as well as any remaining excess material.
    • If the surface is flat, simply scrape it with a spatula to remove any excess material.
    • Cavities and tight angles that act as trap volumes can be cleaned using the ultrasonic cleaner.
  • Wash the parts for 10 more minutes in a clean >99% IPA solution.
  • Carefully check that the part is free from liquid resin residue.
  • Dry the parts with compressed air and place them in a well-ventilated area to allow all absorbed solvent to vacate the part for as long as possible/needed for the part design >4hr minimum or to all solvents are evaporated. Timing depends on the volume & surface area of the part.
    • Indications of uncompleted evaporation are: stickiness, cloudiness, and lower mechanical properties. If during UV post-cure IPA could get locked in the part its will cause previous mentioned defects, and can influence biocompatibility.

UV Post-cure

  • Check the operating performance of the UV-Chamber is up to specification
  • Place the part in a UV-curing oven
    • Duration depends on:
    • Intensity of the UV bulbs
    • Part geometry (surface area)
    • Cleaning beforehand (evaporation solvents)
    • Used for biocompatibility test parts (2x30min with a Philips‘TL-K’40W/05 bulbs (UV-A))
  • Flip over the part half way and make sure all surface area of the part has been exposed to the UV light.

Part-cleaning Procedure – Part II

  • Place the parts in an ultrasonic cleaner, or use gentle stirring, with the Covestro cleaning solution for 5 min @ 37 °C. 
  • Place the part in a second ultrasonic bath with demi water for >5 min @37 °C.
  • Dry the parts with clean compressed air and place them in a well-ventilated area
  • Let the part dry >1hr minimum


Covestro has conducted sterilization tests for the 3D printed materials developed for healthcare purposes. These studies give indications on material changes that can occur during the sterilization process. It remains the responsibility of the device manufacturers to determine the fitness of device in their application. 

The most commonly used methods of sterilizing a medical device are steam autoclave, irradiation, ethylene oxide and hydrogen peroxide gas plasma. 

Steam Autoclave

Steam autoclaving is a widely used, and available as sterilization technique for dental, and medical devices. It is fast, reliable, inexpensive and all healthcare agencies recommend using steam autoclaving whenever possible. 

Disadvantage of this sterilization method in combination with polymer materials is the high temperature, and moisture levels that can lead to deformations during the process. Changes in mechanical properties occur during, and right after the process. Mechanical properties are regained to about 80% in 2hrs. Parts should also be allowed to cool to room temperature, without adding any forces on it after the autoclave cycle to avoid accidentally bending or breaking the part. Thin walls or unsupported areas can deform under its own weight, thicker parts are more stable. In the designs parts can be optimized to prevent these deformations.

Cycle times necessary to achieve sterility vary depending on the items that are being sterilized and the sterilization vessel being used.  Generally, cycle times for flash cycles is 3-5 min or 15 to 30 minutes for standard cycles at temperatures ranging between 121°to 135°Celsius.

Moisture uptake might take place during sterilization, therefore a post-oven treatment under low temperature or keeping the part in a well ventilated room is advised.

Sterilization with autoclave is known to influence biocompatibility of the material extra biocompatibility testing after sterilization is recommended

Low-temperature hydrogen peroxide gas plasma

This low-temperature sterilization process utilizes a concentrated solution of hydrogen peroxide that is injected into a chamber under vacuum. The gas can diffuse throughout the chamber for a period before an electromagnetic field is introduced that creates a gas plasma. The gas plasma breaks down hydrogen peroxide to form free radicals, as well as UV-energy. The free radicals and UV-energy destroy pathogens on the device. Once the plasma begins to lose energy, oxygen and water are formed as by-products.  The process can be repeated as necessary to achieve desired sterility on a given device.  After the final cycle, the chamber is vented to remove oxygen and moisture.  

It should be noted that this type of sterilization may have limitations with certain metals and smaller diameter lumens.  Materials must also be dry for this process and must be packaged in gas-permeable packages.

Hydrogen peroxide gas plasma sterilization can be used with some polymer materials due to the lower temperatures than autoclave.


Irradiation is the use of either an electron beam or gamma rays to sterilize materials.  It is especially useful for sterilizing large, bulk-quantities of disposable items. Dosage or exposure commonly used for irradiation ranges between 20 to 55 kiloGrays (kGy). This method is suitable for some 3D printed polymers, although mechanical properties and color can change during the process. 

Color change is a very common occurrence, but will not necessarily cause problems for the final application. It has been found that even low dose irradiation can cause significant color changes.  Clear 3d printed materials tend to change color from clear to green or pink, while white materials tend to change from white to tan or brown.

Mechanical property changes are common for plastics during irradiation. Often the changes are negligible and sometimes beneficial. Irradiation tends to increase both Young’s Modulus and percent elongation at break, while keeping Izod impact unchanged and in some cases increasing impact strength.

Ethylene Oxide

Polymers can be sensitive to heat, and high moisture environments. Ethylene oxide (EO) is often used to sterilize these materials. EO is an extremely toxic gas and alkylating agent. It works to sterilize materials by disrupting the proteins, DNA and RNA of pathogens, destroying them or interfering with their ability to replicate, and can inactivate all microorganisms.

Items to be sterilized by EO must be completely dry. EO sterilization may require about 12 hours of cycle time, and materials must be packaged in gas-permeable packages. ETO is absorbed by many materials, finding the right aeration parameters is crucial, and depends on material, and geometry of the parts.

Mechanical properties can be moderately affected. The surface of some materials can react with the EO gas leading to toxic residues, therefore careful testing to get the right setting is needed. 

If EO sterilization is used, it is recommended that the parts be thermally post-treated, coated or dyed to create a surface barrier to the reactive EO environment. 

BioClear Sterilization 

ISO 10993-5 has been passed using the following sterilization method:


  • 135°C
  • 5 min

Viscosity Measurement

Depending on the viscosity range of the material you want to test, use the appropriate-sized cup, based on Zahn Cups guidelines. You will also need a long-stem thermometer that mounts onto the Zahn cup handle and a stop watch.


  • Ensure the material in the vat is at part-building temperature.
  • Mount the thermometer on the Zahn cup handle and hold the tip of the thermometer so it is half way up the bowl. The tip of the thermometer should not touch the material in the bowl, but be suspended above it.
  • Turn the thermometer on and set it to Celsius.
  • Lower the machine platform about 100 mm below the material surface.
  • Slowly immerse the Zahn cup at a 45° angle into the vat of material, being careful not to create bubbles, and rest the cup on the platform. Be careful that it does not fall into the material.
  • Monitor the temperature of the material with the thermometer. Wait until the Zahn cup and material have reached the vat temperature. Once the Zahn cup thermometer shows a steady reading, you can take a measurement.
  • Slowly lift the Zahn cup completely out of the material. Start the stopwatch when the top of the cup leaves the material.
  • Watch the stream of material flowing from the hole at the bottom of the cup. When the stream just under the cup breaks and changes from a continuous flow to individual drops, stop the stopwatch.
  • Read the number of seconds on the stopwatch and use the table on the following page to determine the approximate viscosity of the material.
  • Repeat the procedure to obtain at least two values that are close to each other. When finished, turn the thermometer off to save the battery.
  • Record the following data in a chart for each material and machine:
    1. Date
    2. Temperature of material
    3. Readings (seconds)
    4. Viscosity (from table)
  • If the viscosity of the material starts to increase significantly after having been stable for some time, inform Somos® and provide us with the data from the table.
  • Clean the cup and thermometer by wiping them with a paper towel. Wash the cup and thermometer stem with solvent and dry them. Do not remove the long-stem thermometer from the Zahn cup until the stem is completely clean.

Remember: Whenever you have material in your machine, measure and record its viscosity once a week.

Table of approximate viscosity in cps linked to Zahn #4 cup test time

Seconds Approximate Viscosity (CPS)
20 245
22 280
24 310
26 340
28 375
30 410
32 440
34 470
36 505
38 540
40 570
42 600
44 635
46 667
48 700
50 730
52 765
54 800
56 830
58 860
60 895
62 930
64 960
66 990
68 1030
70 1060
72 1090
74 1120
76 1150
78 1190
80 1220
82 1255

Disposal Instructions

Avoid injuring yourself or others

In some areas, partially cured or uncured waste UV material may be classified as hazardous waste, and requires special packaging.

Transportation disposal

Contact the governmental or other body that regulates waste disposal in your area to determine the disposal protocols.

Packaging-Transportation-Disposal Methods

Packaging-Transportation-Disposal methods must prevent any form of human contact with the waste UV material, even if it is classified as nonhazardous or unregulated. This therefore precludes the use of disposal methods that might result in groundwater or surface water contamination.

Solvent Disposal

Solvents should be isolated in a sealed, marked container and disposed of as “hazardous waste” in accordance with all applicable laws and regulations.

Clean-Up Material Disposal

Soiled clothing, empty containers, etc., should be disposed of in accordance with the applicable “hazardous waste” guidelines. If any of these items contain uncured or partially cured UV-curable materials, the disposal method used must prevent any form of human contact, including any that could result in groundwater or surface water contamination.


Below are some examples of common issues and troubleshooting solutions. Consult this part of the guide if you are having difficulties and do not hesitate to contact our Tech Support.

Issue: Delamination

Delamination occurs on the bottom layer of parts at the corners or on part edges.

Solution: Check Blade

Have the physical gap on your re-coating blade checked.

Issue: Roughness

The top surface of the part is not smooth and level.

Solution: Check Re-coating Blade 

This condition is somewhat common and arises due to the viscosity of the material and the presence of debris that may become suspended in it.

Check the re-coating blade to make sure the bottom surface is clean and filter debris from the vat.

It is very important that you maintain the correct material viscosity in your stereolithography machine. The viscosity can increase over time, and this can cause problems in building parts. If the viscosity increase is severe enough, the material may have to be replaced, resulting in significant expense and lost production time.

If increasing viscosity is identified early, the material can, in most cases, be saved. Regularly measuring resin viscosity can provide an early indication of the problem. This must be done even if the machine is not used often, as resin viscosity can change even when the machine is idle.

How can we help?

Get in touch with our experts to discuss how Covestro can help you tap into the full potential of additive manufacturing.