Crystal Clear: The Impact of Finishing Techniques on SLA Parts

Finish #1: As Printed 

The as-printed finish refers to the part’s condition immediately after the printing process, with only the support artifacts removed and sanded flush with the part’s surface. This is the fastest most basic post-processing step, requiring minimal effort: just the removal of the support structures that are used to stabilize the part during the build. This is the ideal finish when assessing geometry or general form. 

• Process: After printing, the part is carefully cleaned and the touchpoints are sanded flush to the surface.  No additional polishing or smoothing is done at this stage, so the natural layer lines and surface remain visible. 
• Transparency: In this state, the part is semi-transparent and can exhibit a slight hazy appearance. Although the Watershed XC 11122 and WaterClear Ultra 10122 resins are both technically transparent in the as-printed state, the presence of micro-imperfections from the printing process can scatter light, creating a semi-transparent SLA resin look – hazy, but still light transmitting.  These imperfections are typically visible when light passes through the part, although they are not tactile; they cannot be felt with the fingers and don’t affect the physical structure of the part. The part below has text at thicknesses of 0.5”, 0.25”, and 0.1”.  
  • Tip: Thinner sections (0.1”-0.25”) appear noticabily clearer than thicker walls (0.5”) due to reduced light scatter. 
• Surface Finish: Visually, you can see some small surface irregularities, particularly where the support artifacts were sanded down. These irregularities are not prominent enough to be felt by touch but may still have a slight impact on the part's overall aesthetic. The lack of additional sanding or post-processing results in a “raw” finish, showcasing the natural characteristics of the printing process.
• Orientation matters: Orientation does affect the transparency of a part, particularly for as-printed SLA finishes. Once a frosted or transparent finish has been applied, the imperfections of the printing process can be minimized. On the images below, the layer lines are more visible in parts that are printed in the Z direction because of how layer stacking affects light refraction. Our engineers at Stratasys Direct can guide optimal orientation based on your clarity or support removal needs. 

Finish #3: Transparent 

For projects requiring the highest clarity – like optical components, light guides, or display models, this is your go-to finish. 

This finish is the most refined post-processing option, designed to achieve a high-clarity 3D printed part.  This coating fills micro-groves and smooths out any remaining texture, transforming the surface to a highly transparent part. 

• Process: The part is manually sanded to remove support artifacts and any visible surface irregularities. This step creates a smooth, consistent surface, which is critical for achieving high transparency. Once sanding is complete, a clear coat is applied to the part to seal the surface and enhance its clarity. The clear coating creates a glossy, reflective finish that maximizes light transmission with minimal distortion.
• Transparency: The transparent finish results in the clearest part of all the post-processing options. Light passes through almost undistorted, giving the part a glass-like look. This finish is ideal for parts that require the highest level of clarity. 
  • Tip: Use this finish when building SLA parts for optical clarity, such as fluid flow analysis, lenses, or clear housings. 
• Surface Finish: The final result is glossy, polished, and highly reflective. The clear coat also provides a protective layer that improves durability and resistance to scratches or damage.