diff --git a/docs/python.md b/docs/python.md
index d702fed9..6c126ea8 100644
--- a/docs/python.md
+++ b/docs/python.md
@@ -629,7 +629,7 @@ $\|\mathbf{r}\|_2 \le \max(\mathrm{rtol}\,\|\mathbf{b}\|_2, \mathrm{atol})$.
 | Parameter | Description |
 |-----------|-------------|
 | `comm` | `Communicator` used for the global reductions. |
-| `fc` | Collection (`GlobalFieldCollection`, `LocalFieldCollection` or `CartesianDecomposition`) on which temporary work fields are created and removed again. |
+| `fc` | Collection (`GlobalFieldCollection`, `LocalFieldCollection` or `CartesianDecomposition`) holding the solver's work fields. They stay registered after the solve, so the next solve on the same collection reuses them instead of allocating anew; their names start with `cg-work`. |
 | `b` | Right-hand side field. Its dtype sets the working precision. |
 | `x` | Initial guess; overwritten with the solution. |
 | `hessp` | Callable `hessp(x, Ax)` writing $\mathbf{A}\mathbf{x}$ into `Ax`. |
@@ -649,6 +649,10 @@ preconditioner is found not to be positive definite, or if a residual becomes
 NaN or infinite. With a `float32` right-hand side, an `rtol` below
 `muGrid.Solvers.FLOAT32_RTOL_FLOOR` (`1e-6`) triggers a `RuntimeWarning`.
 
+Since the work fields remain in `fc`, a `register_field_collection` of that
+collection without `field_names` would write them to the file as well; name
+the fields you want written.
+
 ### conjugate_gradients_pipelined
 
 ```python
diff --git a/language_bindings/python/muGrid/Solvers.py b/language_bindings/python/muGrid/Solvers.py
index a6d51d70..1d6cc680 100644
--- a/language_bindings/python/muGrid/Solvers.py
+++ b/language_bindings/python/muGrid/Solvers.py
@@ -224,8 +224,11 @@ def conjugate_gradients(
         Communicator for parallel processing.
     fc : muGrid.GlobalFieldCollection, muGrid.LocalFieldCollection, or
          muGrid.CartesianDecomposition
-        Collection for creating temporary fields used by the CG algorithm.
-        They are named ``cg#<call>-<role>`` and removed again on return.
+        Collection holding the work fields of the CG algorithm. They are
+        named ``cg-work<depth>-<role>-...`` and stay registered in the
+        collection after the solve for the next one to reuse; pass
+        ``field_names`` to ``FileIONetCDF.register_field_collection`` to
+        leave them out of a file.
     b : muGrid.Field
         Right-hand side vector.
     x : muGrid.Field
@@ -641,7 +644,7 @@ def conjugate_gradients_pipelined(
     ----------
     comm, fc, b, x, hessp, prec, tol, maxiter, timer, rtol, atol
         As for :func:`conjugate_gradients`. Work fields are named
-        ``pcg#<call>-<role>``.
+        ``pcg-work<depth>-<role>-...`` and stay in the collection as well.
     callback : callable, optional
         Called as ``callback(iteration, state_dict)`` at the start of every
         iteration, after the reduction completes, with keys "x", "r", "p",