diff --git a/app/services/dymo_sheet.py b/app/services/dymo_sheet.py
index d691ba2..6b11b82 100644
--- a/app/services/dymo_sheet.py
+++ b/app/services/dymo_sheet.py
@@ -92,6 +92,21 @@ LAYOUTS = [
 ]
 DEFAULT_LAYOUT = 'auto'
 
+# How the page is reduced for a direct thermal printer, which has exactly
+# two states per dot: burnt or not. Doing it here rather than leaving it to
+# the driver is the difference between crisp letters and mush.
+INK_MODES = [
+    ('crisp', 'Crisp black and white (best for text)'),
+    ('photo', 'Dithered (better for part photos)'),
+    ('colour', 'Leave in colour'),
+]
+DEFAULT_INK = 'crisp'
+
+# Anything lighter than this becomes white in crisp mode. High enough to
+# keep antialiased letter edges and the grey meta line, low enough that a
+# part photo's white background stays white.
+INK_THRESHOLD = 186
+
 FORM_MARKER = tape_printer.FORM_MARKER
 
 
@@ -109,9 +124,13 @@ class SheetOptions:
     gap_mm: float = DEFAULT_GAP_MM
     cut_guides: bool = True
     centre: bool = True
-    monochrome: bool = True      # the printer is thermal: no colour at all
+    ink: str = 'crisp'           # crisp | photo | colour - see INK_MODES
     start_at: int = 0            # skip this many slots on the first sticker
 
+    @property
+    def monochrome(self):
+        return self.ink != 'colour'
+
 
 def sheet_options_from_form(form, stock_default=None):
     """SheetOptions from request.form / request.args.
@@ -136,6 +155,10 @@ def sheet_options_from_form(form, stock_default=None):
     if layout not in {key for key, _ in LAYOUTS}:
         layout = DEFAULT_LAYOUT
 
+    ink = form.get('ink') or DEFAULT_INK
+    if ink not in {key for key, _ in INK_MODES}:
+        ink = DEFAULT_INK
+
     return SheetOptions(
         stock=form.get('stock') or stock_default or DEFAULT_STOCK,
         layout=layout,
@@ -143,7 +166,7 @@ def sheet_options_from_form(form, stock_default=None):
         gap_mm=max(0.0, min(10.0, number('gap_mm', DEFAULT_GAP_MM))),
         cut_guides=flag('cut_guides', True),
         centre=flag('centre', True),
-        monochrome=flag('monochrome', True),
+        ink=ink,
         start_at=max(0, min(50, number('start_at', 0, int))),
     )
 
@@ -298,21 +321,39 @@ def render_sheet(placements, options, tape_options, upload_folder, dpi=DPI):
         if place.get('blank') or not place['item'].get('labels'):
             continue
 
-        # Drawn by the same code as the tape labels, then resampled from
-        # 313dpi to the LabelWriter's 300. Keeping one renderer means a
-        # drawer label looks identical whichever printer it came off.
+        # Drawn by the same code as the tape labels, but at the
+        # LabelWriter's own resolution: resampling 313dpi artwork to 300
+        # softens every letter, and a thermal printer has no grey to render
+        # a soft edge with.
         flat = tape_printer.render_fixed(
-            place['item']['labels'], tape_options, upload_folder)
+            place['item']['labels'], tape_options, upload_folder, dpi=dpi)
         if flat.size != (box[2], box[3]):
             flat = flat.resize((box[2], box[3]), Image.LANCZOS)
         canvas.paste(flat, (box[0], box[1]))
 
-    if options.monochrome:
-        # Direct thermal has no colour and no real greys: it is one dot or
-        # no dot. Converting here means we choose how that looks instead of
-        # leaving it to the driver.
-        canvas = canvas.convert('L').convert('RGB')
-    return canvas
+    return reduce_ink(canvas, options.ink)
+
+
+def reduce_ink(image, ink=DEFAULT_INK):
+    """
+    Take the page down to what a direct thermal printer can actually do.
+
+    It has one state per dot: burnt or not. Left in colour or grey, the
+    driver decides how to halftone it, and halftoned text at this size
+    comes out as mush - which is exactly what "legible on screen, not on
+    paper" looks like.
+
+    crisp  threshold, so letters stay solid black with hard edges
+    photo  Floyd-Steinberg, which keeps photographic shading at the cost
+           of speckling the type
+    colour leave it alone and let the driver cope
+    """
+    if ink == 'colour':
+        return image
+    grey = image.convert('L')
+    if ink == 'photo':
+        return grey.convert('1')              # dithered
+    return grey.point(lambda v: 255 if v >= INK_THRESHOLD else 0, mode='1')
 
 
 def _dashed_box(draw, box, dpi, dash_mm=1.2, colour=(170, 170, 170)):
@@ -348,10 +389,13 @@ def render_pdf(plan, options, tape_options, upload_folder, copies=1, dpi=DPI):
                           copies=copies, dpi=dpi)
     if not images:
         return None
+
+    # Mode '1' pages go into the PDF as lossless CCITT G4. Converting to RGB
+    # first would hand Pillow a JPEG instead, and JPEG ringing around 2mm
+    # letters is what made the first printed sheets unreadable.
     buffer = io.BytesIO()
-    images[0].convert('RGB').save(
-        buffer, 'PDF', resolution=dpi, save_all=True,
-        append_images=[i.convert('RGB') for i in images[1:]])
+    images[0].save(buffer, 'PDF', resolution=dpi, save_all=True,
+                   append_images=images[1:])
     buffer.seek(0)
     return buffer
 
@@ -365,6 +409,8 @@ def preview_png(image, scale=7.0):
     target = (max(1, int(px_to_mm(image.width) * scale)),
               max(1, int(px_to_mm(image.height) * scale)))
     buffer = io.BytesIO()
-    image.resize(target, Image.LANCZOS).save(buffer, 'PNG')
+    # A 1-bit page has to go back to greyscale before it is scaled down, or
+    # the browser shows a moire of the dot pattern rather than the label.
+    image.convert('L').resize(target, Image.LANCZOS).save(buffer, 'PNG')
     buffer.seek(0)
     return buffer