diff --git a/.github/.devcontainer/DOCKERFILE_GHCS b/.github/.devcontainer/DOCKERFILE_GHCS
index 058f0a32..10bd9d74 100644
--- a/.github/.devcontainer/DOCKERFILE_GHCS
+++ b/.github/.devcontainer/DOCKERFILE_GHCS
@@ -4,8 +4,8 @@ RUN conda install -n base -c conda-forge mamba
 
 # Here we can install all the dependencies using mamba (as we do in the test scripts)
 
-COPY .devcontainer/uw_environment.yml  /tmp/conda-tmp/
-RUN  mamba env update -n base --file /tmp/conda-tmp/uw_environment.yml 
+COPY .devcontainer/uw_environment.yaml  /tmp/conda-tmp/
+RUN  mamba env update -n base --file /tmp/conda-tmp/uw_environment.yaml 
 
 # Add other dependencies that can't be installed correctly.
 
diff --git a/.github/.devcontainer/uw_environment.yaml b/.github/.devcontainer/uw_environment.yaml
new file mode 120000
index 00000000..8dc54858
--- /dev/null
+++ b/.github/.devcontainer/uw_environment.yaml
@@ -0,0 +1 @@
+../../environment.yaml
\ No newline at end of file
diff --git a/.github/.devcontainer/uw_environment.yml b/.github/.devcontainer/uw_environment.yml
deleted file mode 120000
index 70c7a446..00000000
--- a/.github/.devcontainer/uw_environment.yml
+++ /dev/null
@@ -1 +0,0 @@
-../../environment.yml
\ No newline at end of file
diff --git a/.github/workflows/build_deploy_pdoc.yml b/.github/workflows/build_deploy_pdoc.yaml
similarity index 97%
rename from .github/workflows/build_deploy_pdoc.yml
rename to .github/workflows/build_deploy_pdoc.yaml
index db2ea076..6641fadd 100644
--- a/.github/workflows/build_deploy_pdoc.yml
+++ b/.github/workflows/build_deploy_pdoc.yaml
@@ -21,7 +21,7 @@ jobs:
       - name: Install Conda environment with Micromamba
         uses: mamba-org/setup-micromamba@v2
         with:
-          environment-file: ./environment.yml
+          environment-file: ./environment.yaml
           cache-downloads: true
           cache-environment: true
 
diff --git a/.github/workflows/build_uw3_and_test.yml b/.github/workflows/build_uw3_and_test.yaml
similarity index 95%
rename from .github/workflows/build_uw3_and_test.yml
rename to .github/workflows/build_uw3_and_test.yaml
index 8c0ba18d..775461a2 100644
--- a/.github/workflows/build_uw3_and_test.yml
+++ b/.github/workflows/build_uw3_and_test.yaml
@@ -23,7 +23,7 @@ jobs:
       - name: Install Conda environment with Micromamba
         uses: mamba-org/setup-micromamba@v2
         with:
-          environment-file: ./environment.yml
+          environment-file: ./environment.yaml
           cache-downloads: true
           cache-environment: true
 
diff --git a/.github/workflows/deploy_to_gh_pages.yml.disabled b/.github/workflows/deploy_to_gh_pages.yml.disabled
index e9ed4222..f1ec801a 100644
--- a/.github/workflows/deploy_to_gh_pages.yml.disabled
+++ b/.github/workflows/deploy_to_gh_pages.yml.disabled
@@ -34,7 +34,7 @@ jobs:
     - name: Cache book files
       uses: actions/cache@v1
       env:
-        # Increase this value to reset cache if etc/example-environment.yml has not changed
+        # Increase this value to reset cache if etc/example-environment.yaml has not changed
         CACHE_NUMBER: 0
       with:
         path: |
diff --git a/.github/workflows/docker-image.yml b/.github/workflows/docker-image.yaml
similarity index 100%
rename from .github/workflows/docker-image.yml
rename to .github/workflows/docker-image.yaml
diff --git a/.github/workflows/draft-pdf.yml b/.github/workflows/draft-pdf.yaml
similarity index 100%
rename from .github/workflows/draft-pdf.yml
rename to .github/workflows/draft-pdf.yaml
diff --git a/.github/workflows/envs/build_jb.yml b/.github/workflows/envs/build_jb.yaml
similarity index 100%
rename from .github/workflows/envs/build_jb.yml
rename to .github/workflows/envs/build_jb.yaml
diff --git a/.github/workflows/envs/build_quickstart.yml b/.github/workflows/envs/build_quickstart.yaml
similarity index 100%
rename from .github/workflows/envs/build_quickstart.yml
rename to .github/workflows/envs/build_quickstart.yaml
diff --git a/.github/workflows/envs/build_uw_docs.yaml b/.github/workflows/envs/build_uw_docs.yaml
new file mode 120000
index 00000000..0f9ae9cc
--- /dev/null
+++ b/.github/workflows/envs/build_uw_docs.yaml
@@ -0,0 +1 @@
+../../../environment.yaml
\ No newline at end of file
diff --git a/.github/workflows/envs/build_uw_docs.yml b/.github/workflows/envs/build_uw_docs.yml
deleted file mode 120000
index 7ed7a3b7..00000000
--- a/.github/workflows/envs/build_uw_docs.yml
+++ /dev/null
@@ -1 +0,0 @@
-../../../environment.yml
\ No newline at end of file
diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yaml
similarity index 96%
rename from .github/workflows/publish.yml
rename to .github/workflows/publish.yaml
index be260e01..e53126a3 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yaml
@@ -22,8 +22,8 @@ jobs:
         uses: mamba-org/setup-micromamba@v2
         with:
           #micromamba-version: "1.5.6-0" # any version from https://github.com/mamba-org/micromamba-releases
-          #environment-file: .github/workflows/envs/build_quickstart.yml
-          environment-file: ./environment.yml
+          #environment-file: .github/workflows/envs/build_quickstart.yaml
+          environment-file: ./environment.yaml
           init-shell: bash
           cache-environment: true
           post-cleanup: "all"
diff --git a/Dockerfile b/Dockerfile
deleted file mode 100644
index b0032458..00000000
--- a/Dockerfile
+++ /dev/null
@@ -1,48 +0,0 @@
-# syntax=docker/dockerfile:1.7-labs
-
-### how to build docker image
-
-# (1) run from the underworld3 top directory
-# podman build . \
-# --rm \
-# -f ./.github/Dockerfile \
-# --format docker \
-# -t underworldcode/underworld3:0.99
-
-### needs the --format tag to run on podman
-
-FROM docker.io/mambaorg/micromamba:2.3.0
-
-USER $MAMBA_USER
-ENV NB_HOME=/home/$MAMBA_USER
-
-# create the env
-COPY --chown=$MAMBA_USER:$MAMBA_USER environment.yml /tmp/env.yaml
-RUN micromamba install -y -n base -f /tmp/env.yaml && \
-    micromamba clean --all --yes
-
-# activate mamba env during `docker build`
-ARG MAMBA_DOCKERFILE_ACTIVATE=1
-
-# install UW3
-WORKDIR /tmp
-COPY --exclude=**/.git \
-     --chown=$MAMBA_USER:$MAMBA_USER \
-     . /tmp/underworld3
-WORKDIR /tmp/underworld3
-
-RUN pip install --no-build-isolation --no-cache-dir .
-
-# copy files across
-RUN mkdir -p $NB_HOME/workspace
-
-COPY --chown=$MAMBA_USER:$MAMBA_USER ./tests   $NB_HOME/Underworld/tests
-
-EXPOSE 8888
-WORKDIR $NB_HOME
-USER $MAMBA_USER
-
-# Declare a volume space
-VOLUME $NB_HOME/workspace
-
-CMD ["jupyter-lab", "--no-browser", "--ip=0.0.0.0"]
diff --git a/README.md b/README.md
index 600a681a..2fa74f61 100644
--- a/README.md
+++ b/README.md
@@ -41,9 +41,13 @@ The quickest option is **not to install** anything but try the binder demo above
 
 If do you want to install the code on your own machine, we recommend using `miniconda` and `mamba`. Create a separate virtual environment and install the code from source. More details on how to do that are in the [Installation Instructions](https://underworldcode.github.io/underworld3/development/_quickstart/Installation.html)
 
-## References 
+## References and Archives 
 
 The canonical releases of the code can be found at [zenodo.org](https://doi.org/10.5281/zenodo.16810746).
 
 [![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.16810747.svg)](https://doi.org/10.5281/zenodo.16810746)
 
+There is a [publication in the Journal of Open Source Software](https://joss.theoj.org/papers/4f7a1ed76bde560968c246fa8eff778d) 
+([doi:10.21105/joss.07831](https://doi.org/10.21105/joss.07831)) that can be cited when using the software. 
+
+[![status](https://joss.theoj.org/papers/4f7a1ed76bde560968c246fa8eff778d/status.svg)](https://joss.theoj.org/papers/4f7a1ed76bde560968c246fa8eff778d)
diff --git a/docs/developer/container/Containerfile b/docs/developer/container/Containerfile
new file mode 100644
index 00000000..3e4b1816
--- /dev/null
+++ b/docs/developer/container/Containerfile
@@ -0,0 +1,59 @@
+# syntax=docker/dockerfile:1.7-labs
+
+### how to build Underworld3 image
+### MUST run from the underworld3 top directory
+#   podman build . --rm \
+#       --format docker \
+#       -f ./docs/developer/container/Containerfile \ 
+#       -t underworldcode/underworld3:<version-id>
+#
+### requires the '--format docker' to run on podman, but no under docker.
+#
+#
+### Example usage (taken from - https://jupyter-docker-stacks.readthedocs.io/en/latest/using/running.html#using-the-podman-cli )
+# uid=57439
+# gid=57439
+
+# subuidSize=$(( $(podman info --format "{{ range .Host.IDMappings.UIDMap }}+{{.Size }}{{end }}" ) - 1 ))
+# subgidSize=$(( $(podman info --format "{{ range .Host.IDMappings.GIDMap }}+{{.Size }}{{end }}" ) - 1 ))
+# podman run   -it --rm   -p 10000:8888   -v "${HOME}/uw_space":/home/mambauser/host   --uidmap $uid:0:1 --uidmap 0:1:$uid --uidmap $(($uid+1)):$(($uid+1)):$(($subuidSize-$uid))   --gidmap $gid:0:1 --gidmap 0:1:$gid --gidmap $(($gid+1)):$(($gid+1)):$(($subgidSize-$gid)) underworldcode/underworld3:<version-id>
+
+FROM docker.io/mambaorg/micromamba:2.3.0
+
+# install os requirements for headless pyvista
+USER root
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    xvfb \
+    libgl1-mesa-dev \
+    && rm -rf /var/lib/apt/lists/*
+USER $MAMBA_USER
+
+# create the conda environment with all dependencies 
+# see https://micromamba-docker.readthedocs.io/en/latest/quick_start.html#quick-start
+COPY --chown=$MAMBA_USER:$MAMBA_USER environment.yaml /tmp/env.yaml
+RUN micromamba install -y -v -n base -f /tmp/env.yaml && \
+    micromamba clean --all --yes
+
+# activate mamba env during podman build
+ARG MAMBA_DOCKERFILE_ACTIVATE=1
+
+# pyvista - taken from pyvista docker files
+# see https://github.com/pyvista/pyvista/tree/main/docker
+RUN pip install --no-cache-dir --extra-index-url https://wheels.vtk.org vtk-osmesa
+
+# install UW3
+COPY --chown=$MAMBA_USER:$MAMBA_USER \
+     --exclude=**/.git \
+     . /home/$MAMBA_USER/underworld3
+WORKDIR /home/$MAMBA_USER/underworld3
+RUN pip install --no-build-isolation --no-cache-dir .
+
+# allow jupyterlab for ipyvtk
+ENV PYVISTA_OFF_SCREEN=true
+ENV JUPYTER_ENABLE_LAB=yes
+ENV PYVISTA_TRAME_SERVER_PROXY_PREFIX='/proxy/'
+
+WORKDIR /home/$MAMBA_USER/
+
+EXPOSE 8888
+CMD ["jupyter-lab", "--no-browser", "--ip=0.0.0.0"]
diff --git a/docs/developer/container/README.md b/docs/developer/container/README.md
new file mode 100644
index 00000000..6d7a7788
--- /dev/null
+++ b/docs/developer/container/README.md
@@ -0,0 +1,22 @@
+The `Containerfile` is used to build the container and can be used with docker or podman. 
+At present only amd64 architecture is built, because vtk-osmesa isn't available for arm by default. This may change in future, or we could build vtk-osmesa from source (see https://docs.pyvista.org/extras/building_vtk.html)
+
+Example use, must be run from repository root.
+```bash
+   podman build . --rm \
+       --format docker \
+       -f ./docs/developer/container/Containerfile \ 
+       -t underworldcode/underworld3:foobar
+```
+
+The `launch-container.sh` is a script for launching the container using `podman` only. Podman is the preferred container runner because of `rootless` support.
+Expect the script to take a minute or so to load as permissions are updated. 
+Host port 10000 will run the container's default jupyter server. See script for details. 
+
+Useful links:
+- Container stacks with podman - https://jupyter-docker-stacks.readthedocs.io/en/latest/using/running.html#using-the-podman-cli
+- Micromamba images - https://micromamba-docker.readthedocs.io/en/latest/quick_start.html#quick-start
+- Pyvista containers: 
+    - https://github.com/pyvista/pyvista/tree/main/docker
+    - https://dev.pyvista.org/getting-started/installation#running-on-mybinder
+
diff --git a/docs/developer/container/launch-container.sh b/docs/developer/container/launch-container.sh
new file mode 100755
index 00000000..3d2015a4
--- /dev/null
+++ b/docs/developer/container/launch-container.sh
@@ -0,0 +1,61 @@
+#!/usr/bin/env bash
+
+### Used for running the underworld3 container.
+# This requires 'podman', not docker. Install podman from 
+#   https://podman.io/docs/installation
+#
+# Once podman is installed and available on the command line, run with 
+#   ./launch-container.sh
+#
+# this will launch a container with a jupyter server running on
+#   http://localhost:10000
+# Also, the machine (host) directory 
+#   $HOME/uw_space
+# will be mapped into the container under /home/mambauser/host.
+# for transfering data to/from the container.
+#
+##
+
+set -x 
+
+# check to see if $HOME/uw_space exists, if not create it
+mkdir -p $HOME/uw_space
+
+# Set 'mambauser' uid/gid from base image, 'mambaorg/micromamba'
+uid=57439
+gid=57439
+
+subuidSize=$(( $(podman info --format "{{ range .Host.IDMappings.UIDMap }}+{{.Size }}{{end }}" ) - 1 ))
+subgidSize=$(( $(podman info --format "{{ range .Host.IDMappings.GIDMap }}+{{.Size }}{{end }}" ) - 1 ))
+
+# This will set an jupyter server on HOST port 10000
+# the uidmap / gidmap make the container UID compatible with the host system.
+# DO NOT run the following command with root, this is explain further below.
+podman run -it --rm \
+  -p 10000:8888     \
+  --uidmap $uid:0:1 \
+  --uidmap 0:1:$uid \
+  --uidmap $(($uid+1)):$(($uid+1)):$(($subuidSize-$uid)) \
+  --gidmap $gid:0:1 \
+  --gidmap 0:1:$gid \
+  --gidmap $(($gid+1)):$(($gid+1)):$((subgidSize-$gid)) \
+  -v "${HOME}/uw_space":/home/mambauser/host \
+  docker.io/underworldcode/underworld3:development 
+
+## Description of rootless podman and uidmap/gidmap.
+# Rootless podman allows a non-root user to run a container without elevated permissions.
+# DO NOT use `sudo` to execute the above `podman run` command
+# This is unlike rootful podman, or docker, thus it's more secure but has some complexity in the for of permission namespaces
+# the host and container permissions are elegantly 'namespaced' to two id mappings.
+#  1. host ids -> intermediate (/etc/subuid)
+#  2. intermediate -> container ids (uidmaps arguments)
+# 
+# In the above `podman run` we set uidmaps to allow for straight forward container / host directory bindmounts
+# container UID 57439 -> host UID 0 (if podman rootless this is host UID)
+# container UID 0-57438 -> host UID 1-57439
+# container UID 57440-delta -> host UID 57440-delta
+# as the container would have root accesson the host.
+# The $uid -> host UID 0 assumes podman "rootless" access, i.e. the host UID executing the container.
+# All other UIDs in the container are mapped to something different.
+#
+# This **MUST** be run without sudo, otherwise the host UID would be root.
diff --git a/docs/developer/docker/underworld3.dockerfile b/docs/developer/docker/underworld3.dockerfile
deleted file mode 100644
index 8209e23d..00000000
--- a/docs/developer/docker/underworld3.dockerfile
+++ /dev/null
@@ -1,47 +0,0 @@
-### how to build docker image
-
-# (1) run from the underworld3 top directory
-# podman build . \
-# --rm \
-# -f ./docs/developer/docker/underworld3.dockerfile \
-# --format docker \
-# -t underworldcode/underworld3:0.9.9
-
-### needs the --format tag to run on podman
-
-FROM docker.io/mambaorg/micromamba:debian11-slim
-
-
-USER $MAMBA_USER
-ENV NB_HOME=/home/$MAMBA_USER
-
-### create the env
-COPY --chown=$MAMBA_USER:$MAMBA_USER environment.yml /tmp/env.yaml
-RUN micromamba install -y -n base -f /tmp/env.yaml && \
-    micromamba clean --all --yes
-
-# ### activate env and install
-ARG MAMBA_DOCKERFILE_ACTIVATE=1
-
-
-# ### install UW3
-WORKDIR /tmp
-COPY --chown=$MAMBA_USER:$MAMBA_USER . /tmp/underworld3
-WORKDIR /tmp/underworld3
-
-### install uw3 using pip
-RUN pip install --no-build-isolation .
-
-#### copy files across
-RUN mkdir -p $NB_HOME/workspace
-
-COPY --chown=$MAMBA_USER:$MAMBA_USER ./tests   $NB_HOME/Underworld/tests
-
-EXPOSE 8888
-WORKDIR $NB_HOME
-USER $MAMBA_USER
-
-# Declare a volume space
-VOLUME $NB_HOME/workspace
-
-CMD ["jupyter-lab", "--no-browser", "--ip='0.0.0.0'"]
diff --git a/docs/user/Installation.qmd b/docs/user/Installation.qmd
index a66fa443..f9e34afa 100644
--- a/docs/user/Installation.qmd
+++ b/docs/user/Installation.qmd
@@ -17,7 +17,7 @@ The `underworld3` build / run-time dependencies can be installed using
 ```bash
     (base) % git clone -b development --single-branch https://github.com/underworldcode/underworld3 /path/to/underworld3
     (base) % cd /path/to/underworld3
-    (base) % mamba env create -n uw3 -f environment.yml
+    (base) % mamba env create -n uw3 -f environment.yaml
     (base) % mamba activate uw3
 
     (uw3) % compile.sh
@@ -32,7 +32,7 @@ installed `PETSc` and `petsc4py`.
 ```bash
     (base) % git clone -b development --single-branch https://github.com/underworldcode/underworld3 /path/to/underworld3
     (base) % cd /path/to/underworld3
-    (base) % mamba env create -n uw3p -f environment.yml
+    (base) % mamba env create -n uw3p -f environment.yaml
     (base) % mamba activate uw3p
 
     (uw3p) % mamba remove petsc4py
diff --git a/docs/user/_quarto.yml b/docs/user/_quarto.yaml
similarity index 100%
rename from docs/user/_quarto.yml
rename to docs/user/_quarto.yaml
diff --git a/environment.yml b/environment.yaml
similarity index 64%
rename from environment.yml
rename to environment.yaml
index 68e641dc..ea6b02b8 100644
--- a/environment.yml
+++ b/environment.yaml
@@ -2,7 +2,7 @@ name: uw3
 channels:
   - conda-forge
 dependencies:
-  - python=3.11
+  - python <= 3.11
   - compilers
   - mpich
   - petsc=3.21.5
@@ -19,21 +19,25 @@ dependencies:
   - ipython
   - mpi4py
   - h5py=*=mpi*
-  - trame
-  - ipywidgets
   - gmsh
   - python-gmsh
   - python-xxhash
-  - jupyterlab
   - jupytext
-  - trame-vtk
-  - trame-vuetify
   - pygments
   - pint
+  - cmocean
+  - colorcet
+  - imageio
+  - imageio-ffmpeg
+  - ipywidgets<9.0.0
+  - jupyter-server-proxy
+  - jupyterlab<5.0.0
+  - trame>=2.5.2
+  - trame-vtk>=2.5.8
+  - trame-vuetify>=2.3.1
+  - trimesh
   - typeguard
   - pip
   - pip:
       - rich<14
       - meshio
-      - pygmsh
-        # - gmsh-api # is this used still in UW?
diff --git a/src/underworld3/ckdtree.pyx b/src/underworld3/ckdtree.pyx
index 34adb24e..cb3252f9 100644
--- a/src/underworld3/ckdtree.pyx
+++ b/src/underworld3/ckdtree.pyx
@@ -215,9 +215,9 @@ cdef class KDTree:
             i = i.reshape(-1)
 
         if sqr_dists:
-            return numpy.sqrt(d), i
-        else:
             return d, i
+        else:
+            return numpy.sqrt(d), i
 
 
 ## A general point-to-point rbf interpolator here
diff --git a/src/underworld3/cython/petsc_generic_snes_solvers.pyx b/src/underworld3/cython/petsc_generic_snes_solvers.pyx
index a2070f00..b42b1668 100644
--- a/src/underworld3/cython/petsc_generic_snes_solvers.pyx
+++ b/src/underworld3/cython/petsc_generic_snes_solvers.pyx
@@ -700,7 +700,7 @@ class SNES_Scalar(SolverBaseClass):
                 print(" - field:      {}".format(bc.f_id))
                 print(" - components: {}".format(bc.components))
                 print(" - boundary:   {}".format(bc.boundary))
-                print(" - fn:         {} ".format(bc.fn))
+                print(" - fn:         {} ".format(bc.fn_f))
 
             boundary = bc.boundary
             value = mesh.boundaries[bc.boundary].value
@@ -846,38 +846,39 @@ class SNES_Scalar(SolverBaseClass):
             #     continue
 
             if bc.fn_f is not None:
-
+                
                 bd_F0  = sympy.Array(bc.fn_f)
-                self._bd_f0 = sympy.ImmutableDenseMatrix(bd_F0)
-
-                G0 = sympy.derive_by_array(self._bd_f0, U)
-                G1 = sympy.derive_by_array(self._bd_f0, self.Unknowns.L)
+                bc.fns["u_f0"] = sympy.ImmutableDenseMatrix(bd_F0)
+                
+                G0 = sympy.derive_by_array(bd_F0, U)
+                G1 = sympy.derive_by_array(bd_F0, L)
 
-                self._bd_G0 = sympy.ImmutableMatrix(G0) # sympy.ImmutableMatrix(sympy.permutedims(G0, permutation).reshape(dim,dim))
-                self._bd_G1 = sympy.ImmutableMatrix(G1.reshape(dim)) # sympy.ImmutableMatrix(sympy.permutedims(G1, permutation).reshape(dim,dim*dim))
+                bc.fns["uu_G0"] = sympy.ImmutableMatrix(G0.reshape(1, 1)) 
+                bc.fns["uu_G1"] = sympy.ImmutableMatrix(G1.reshape(dim, 1))
 
-                fns_bd_residual += [self._bd_f0]
-                fns_bd_jacobian += [self._bd_G0, self._bd_G1]
+                fns_bd_residual += [bc.fns["u_f0"]]
+                fns_bd_jacobian += [bc.fns["uu_G0"], bc.fns["uu_G1"]]
 
+            # Similar to SNES_Vector, will leave these out for now, perhaps a different user-interface altogether is required for flux-like bcs
 
-            if bc.fn_F is not None:
+            # if bc.fn_F is not None:
 
-                bd_F1  = sympy.Array(bc.fn_F).reshape(dim)
-                self._bd_f1 = sympy.ImmutableDenseMatrix(bd_F1)
+            #     bd_F1  = sympy.Array(bc.fn_F).reshape(dim)
+            #     self._bd_f1 = sympy.ImmutableDenseMatrix(bd_F1)
 
-                G2 = sympy.derive_by_array(self._bd_f1, U)
-                G3 = sympy.derive_by_array(self._bd_f1, self.Unknowns.L)
+            #     G2 = sympy.derive_by_array(self._bd_f1, U)
+            #     G3 = sympy.derive_by_array(self._bd_f1, self.Unknowns.L)
 
-                self._bd_uu_G2 = sympy.ImmutableMatrix(G2.reshape(dim)) # sympy.ImmutableMatrix(sympy.permutedims(G2, permutation).reshape(dim*dim,dim))
-                self._bd_uu_G3 = sympy.ImmutableMatrix(G3.reshape(dim,dim)) # sympy.ImmutableMatrix(sympy.permutedims(G3, permutation).reshape(dim*dim,dim*dim))
+            #     self._bd_uu_G2 = sympy.ImmutableMatrix(G2.reshape(dim)) # sympy.ImmutableMatrix(sympy.permutedims(G2, permutation).reshape(dim*dim,dim))
+            #     self._bd_uu_G3 = sympy.ImmutableMatrix(G3.reshape(dim,dim)) # sympy.ImmutableMatrix(sympy.permutedims(G3, permutation).reshape(dim*dim,dim*dim))
 
-                fns_bd_residual += [self._bd_f1]
-                fns_bd_jacobian += [self._bd_G2, self._bd_G3]
+            #     fns_bd_residual += [self._bd_f1]
+            #     fns_bd_jacobian += [self._bd_G2, self._bd_G3]
 
 
         self._fns_bd_residual = fns_bd_residual
         self._fns_bd_jacobian = fns_bd_jacobian
-
+        
         # generate JIT code.
         # first, we must specify the primary fields.
         # these are fields for which the corresponding sympy functions
@@ -1284,7 +1285,7 @@ class SNES_Vector(SolverBaseClass):
                 print(" - field:      {}".format(bc.f_id))
                 print(" - component:  {}".format(bc.components))
                 print(" - boundary:   {}".format(bc.boundary))
-                print(" - fn:         {} ".format(bc.fn))
+                print(" - fn:         {} ".format(bc.fn_f))
 
             boundary = bc.boundary
             value = mesh.boundaries[bc.boundary].value
diff --git a/tests/test_1000_poissonNaturalBC.py b/tests/test_1000_poissonNaturalBC.py
new file mode 100644
index 00000000..a3bb7e9c
--- /dev/null
+++ b/tests/test_1000_poissonNaturalBC.py
@@ -0,0 +1,77 @@
+import pytest
+import underworld3 as uw
+import sympy
+import numpy as np
+
+'''
+Unit test for Natural BCs in a Poisson (scalar) problem. 
+'''
+
+res   = 16
+
+width   = 1
+height  = 1
+
+minX, maxX = 0, width
+minY, maxY = 0, height
+
+mesh_simp_reg = uw.meshing.UnstructuredSimplexBox(  minCoords   = (minX, minY), 
+                                                    maxCoords   = (maxX, maxY), 
+                                                    cellSize    = 1 / res, 
+                                                    qdegree     = 3,
+                                                    regular = True)
+mesh_simp_irreg = uw.meshing.UnstructuredSimplexBox(minCoords   = (minX, minY), 
+                                                    maxCoords   =(maxX, maxY), 
+                                                    cellSize    = 1 / res, 
+                                                    regular     = False)
+mesh_quad = uw.meshing.StructuredQuadBox(minCoords  = (minX, minY), 
+                                        maxCoords   = (maxX, maxY), 
+                                        elementRes  = (res, res))
+
+@pytest.mark.parametrize("mesh", 
+                         [mesh_simp_reg,
+                          mesh_simp_irreg,
+                          mesh_quad]
+)
+
+def test_poisson_natural_bc(mesh):
+
+    T_soln = uw.discretisation.MeshVariable("T", mesh, 1, degree = 2)
+
+    poisson = uw.systems.Poisson(mesh = mesh, 
+                                u_Field = T_soln, 
+                                degree = 2,
+                                verbose = False,
+                                )
+    
+    poisson.constitutive_model = uw.constitutive_models.DiffusionModel
+    poisson.constitutive_model.Parameters.diffusivity = 1.0
+    poisson.petsc_options.delValue("ksp_monitor")
+
+    # set the source based on analytical solution
+    x, y = mesh.N.x, mesh.N.y
+    ana_soln = (x**2) * y 
+
+    #poisson.tolerance = 1e-6 # increase tolerance to decrease atol in allclose
+    poisson.f = -2 * y
+
+    poisson.add_natural_bc(0.0, "Left")
+    poisson.add_natural_bc([2*y], "Right")
+    poisson.add_natural_bc([x**2], "Bottom")
+    poisson.add_natural_bc([x**2], "Top")
+
+    poisson.add_dirichlet_bc(0.0, "Left")
+    poisson.add_dirichlet_bc([y], "Right")
+    poisson.add_dirichlet_bc(0.0, "Bottom")
+    poisson.add_dirichlet_bc([x**2], "Top")
+
+    poisson.solve()
+
+    with mesh.access():
+        num = T_soln.data[:].squeeze()
+        ana = uw.function.evaluate(ana_soln, T_soln.coords)
+
+    assert np.allclose(ana, num, atol = 1e-4), "Numerical and analytical solutions differ!"
+
+    del poisson 
+    del mesh
\ No newline at end of file