Project HighLighTED

The HighLighter Thermal Extraction Device

A simple, low-cost, nearly tool-less, 
glass, compact, and highly effective 
Open Source Halogen Log
By the 

Scientifically Higher Design Collective


RedEye FlightControl (
Khelek41Girl (
Paniczeezily (AWistfulNihilist)

Mission: A community driven, open source, effective DIY heater that anyone can fully assemble with no soldering or complex tools required!

Goals: Adequately tuned thermal mass, standard off-the-shelf parts, repairable, compact, low cost, compatible with industry standard 12V 5A VVPS



The HIGHLighTED ( High-Lighter Thermal Extraction Device) is a community designed open source 12 volt glass-core heater inspired by glass beaded heaters like the G43 and Glass Symphony. The HLT uses a quartz-halogen lamp surrounded by glass beads to achieve quick, deep extractions comparable to some of the best devices on the market. 


The HIGHLighTED incorporates many features and design considerations to make sourcing parts, assembling, powering, and using the heater as easy and convenient as possible, while providing a good compromise between power demand and efficiency. The heater design includes several key elements to enhance the experience:

  • The heater cover is a simple 19/22 or 19/26 female joint blank allowing the heater to be placed directly on top of a basket, stem, or 19/22 adapter  without restricting the airflow. These joints are low cost, modular, and easy to find. 
  • A 10mm dia GY6.35 Bi-Pin 50 watt halogen lamp with quartz bulb provides a clean heat source
  • 7.2 grams of 3mm boro or soda lime laboratory grade boiling stones provide the most optimized use of volume for thermal mass

Advantages of Glass Beads

Glass beads provide a number of benefits:

  • Thermal Capacity
    • Allows the HighlighTED to maintain a more stable temperature while heating
    • Refractory period greatly reduced between uses
  • High Surface area of beads, cover, bulb
    • Effectively and very rapidly heats the passing fluids
  • Diffusion of air
    • Spreads heated fluids effectively across the oven, creating even heat flow, and minimizing hotspotting.

The glass beads in the HighlighTED are 3mm diameter soda-lime or borosilicate boiling stones. Both materials are acceptable and should perform similarly. 3mm is the most ideal size for airflow, thermal expansion play, and self-centering bulb reasons.  More exotic materials do not noticeably improve the performance.

Advantages of the Halogen Bulb Core

Halogen bulbs make low cost and efficient heaters because nearly 90% of the energy consumed is radiated as thermal waste. Testing has shown that these bulbs only need to consume about 16 to 19 watts at around 6.6 to 6.8 volts for exemplary results. 

  • The glass heater cover and ceramic bulb socket are both very poor conductors, trapping heat right where it is needed 
  • The thermal transfer properties of glass/quartz encourage even temperatures across the entire heater when at operating temperature
  • The heat waste of a halogen bulb greatly reduces thermal sag, refractory period, and cold startup times

Modular, standardized, and simple construction

The use of inexpensive, commonly available commodity laboratory equipment along with a simple light bulb makes sourcing parts and building easy. Scientific and commercial standards ensure the parts will be available for the foreseeable future, ensuring product longevity and reparability.

  • Standard heater cover is simply a 19/26ST 22x2mm x 110mm blank
  • ¾” 60Mesh SS retainer screen, hand-convexed, friction-fit
  • GY6.35 BiPin 10mm Dia Halogen Bulb formfactor + Ceramic base
  • 12Volt 5amp Variable voltage PS & 5.5mm receptacle Compatible 

Operation, Best Practices, and Safety

Bulb and glass safety

  • Never handle a hot bulb or hot glass - always wait 10+ minutes for the unit to cool down before handling heated areas/parts
  • Always clean the quartz bulb with iso prior to installation. Doing so will prolong the life of the bulb and help prevent odors and tastes at startup
  • Never use a bulb other than the recommended GY6.35 bi-pin halogen quartz
  • Never use a bulb in a size other than 10mm diameter
  • Never use beads in a size other than 3mm diameter
  • Never bang, jar, or impact the heater. 
  • Never pull on the wire harness unless assisting core pack out from joint
  • Do not leave the hot or illuminated bulb on organic material for an extended period of time, it may heat enough to pyrolyze or ignite.

Handling safety

  • Never handle the heater near the lit portion or joint end
  • Never apply a clamp, or rest on a stand in a manner that exposes the heater core area rest on any non-heat-proof surface
  • Never place the heater in a position where it can be bumped, jarred, tipped over, broken, dropped, or pulled off a surface by its cord
  • Never apply excessive force to the glass components at any temperature
  • Never use force to adjust a heater, hot or otherwise
  • Never use water to clean the base/wires/bulb
  • Never apply water or other liquids to hot glass
  • Never attempt to clean a fully assembled unit
  • Never alter or modify parts


  • Allow unit to heat fully at 6.5 volts in the VVPS for 10-15m
  •  when ready to inhale, place heater core atop 18mm male joint with a pre-loaded basket screen
    • Unit functions on-demand 
    • Remove heater from material just prior to the end of inhaling to reduce vapor condensing in core
  • Heater Joint does not need to be spun, but can be, for more even, quicker extraction
  • Heater can be removed for full convection mode, or left on WPA for hybrid mode (convection dominant plus radiant)

Best Practices

  • Clean all glass pieces with iso prior to installation
    • Ensure you fully remove the text printed on the lamp
  • Visibly inspect unit prior to every use to ensure parts are secure
  • Do not run unit over the recommended voltages to ensure material and bulb safety
  • Leave your power supply on the same setting and unplug to power off
  • A silicone mat makes a great non-slip surface



Dimensional Characteristics:

bulb dimensions



Bulb: Quartz GY6.35 BiPin Halogen Lamp - 12Volt 50Watt

Socket: Ceramic + SpringClip + Silicone shielded copper wire

Large O-Ring: 2x M3x12 (12mm ID x 3mm CS) 70 Durometer Silicone

Small O-Ring: 1x #111  70 Durometer Silicone

Shield O-Ring: 3x M4x22 70-Durometer Silicone

ProForma screen: 1⅛ “ 30-Mesh Stainless Steel  (Formed through a ¾” Die or hand-fashioned)

DC Power Jack: 5.5mm female receptacle - HIGH QUALITY required

Opaque black (first) or Cobalt blue (second) recommended

F:19/22 or 19/26, ~18mm ID ~22mm OD glass, ~2mm wall

M wand:19/22 w/ ½” opening, blank ~16mm OD, ~12.3mm ID, ~120+mm

Power Receptacle: 5.5mm x 2.1mm KASTAR brand female DC jack

Screen: 1 ⅛ ” 30Mesh Stainless Steel ProForma basket, 19mm dia

Thermal Mass: 7.2g (~178) 3.0mm Soda-Lime Laboratory boiling stones 

Basket: ½” rimmed/crimped basket pipe screen



By buying, using, building, or otherwise interacting with the parts specified in this documentation, you fully release all liability and hold harmless REFC Labs LLC and SHDC with the understanding and full acceptance of the responsibilities and the inherent danger of handling hot, fragile, and electrified parts. Neither REFC labs LLC nor the members of SHDC will be held liable for any injury, loss of property, tangible or intangible damages, or other any other negative consequence of working with experimental kit hardware. It is up to the user to fully understand the risks involved in working with these materials. REFC Labs LLC provides these materials as a kit as a convenience to the enduser/customer/consumer, however the enduser /customer/consumer is fully responsible for the building and use of these parts. 

Copyright 2021 REFC Labs LLC

Project HighLighTED, The HighLighter, and its full suite of documentation, bill of materials, and design likeness are licensed under Creative Commons Attribution NonCommercial ShareAlike license. 

You are free to:

  • Adapt — remix, transform, and build upon the material

Under the following terms:

  • Attribution  You must give appropriate credit, and provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.

  • NonCommercial — You may not use the material for commercial purposes.

  • ShareAlike — If you remix, transform, or build upon the material, you must distribute your contributions under the same license as the original.