diff --git a/app.py b/app.py
index ac52959..7082dd2 100755
--- a/app.py
+++ b/app.py
@@ -1,12 +1,24 @@
 #!/usr/bin/env python
 
-from flask import Flask, redirect, request, render_template, send_from_directory
+from flask import Flask, redirect, request, render_template, send_from_directory, session
 import json
+import os
 from os.path import join
+import sqlite3
+from typing import Optional
 import uuid
 from . import db, config, scanner, calibration
 
 app = Flask(__name__)
+app.config['SECRET_KEY'] = os.urandom(20).hex()
+
+
+def get_calibration(conn: sqlite3.Connection) -> Optional[db.Calibration]:
+    calibration_id = session.get('calibration_id', None)
+    if calibration_id is None:
+        return None
+
+    return db.Calibration.get_from_id(calibration_id, conn)
 
 
 @app.route("/")
@@ -28,7 +40,7 @@ def create_object():
 def object(id: int):
     conn = db.get()
     object = db.Object.get_from_id(id, conn)
-    return render_template('object.html', object=object)
+    return render_template('object.html', object=object, calibration=get_calibration(conn))
 
 
 @app.route('/scan/<id>')
@@ -38,19 +50,13 @@ def scan(id: int):
     return render_template('object.html', object=object)
 
 
-@app.route("/calibrate/<id>")
-def calibrate(id: int):
+@app.route("/calibrate/")
+def calibrate():
     conn = db.get()
-    object = db.Object.get_from_id(id, conn)
-    if object.calibration_id is None:
-        with conn:
-            calibration = db.Calibration.create(conn)
-            object.calibration_id = calibration.id
-            object.save(conn)
-    else:
-        calibration = object.calibration(conn)
-
-    return render_template('calibrate.html', object=object, calibration=calibration, leds=config.LEDS_UUIDS)
+    with conn:
+        calibration = db.Calibration.create(conn)
+        session['calibration_id'] = calibration.id
+    return render_template('calibrate.html', calibration=calibration)
 
 
 @app.route("/api/preview/<id>")
diff --git a/templates/calibrate.html b/templates/calibrate.html
index f8d99ae..184c808 100644
--- a/templates/calibrate.html
+++ b/templates/calibrate.html
@@ -30,7 +30,7 @@
             </div>
         </div>
         <progress id="progress-bar" class="progress is-link" style="display: none;" value="0" max="1000"></progress>
-        <div id="calibrate" {% if calibration.state == 0 %}style="display: none;"{% endif %}>
+        <div id="calibrate" style="display: none;">
             <p>Si les données d'étalonnage conviennent, appuyez sur le bouton ci-dessous pour procéder à l'étalonnage du scanner</p>
             <button id="calibrate-button" class="button is-link">Étalonner le scanner</button>
             <p id="calibration-info"></p>
@@ -58,11 +58,11 @@
     previewButton.addEventListener('click', async () => {
         buttons.forEach(x => x.setAttribute('disabled', 'disabled'));
         previewButton.classList.add('is-loading');
-        let response = await fetch('/api/preview/{{ object.id }}');
+        let response = await fetch('/api/preview/{{ calibration.id }}');
         let uuid = await response.text();
 
         if (response.status >= 200 && response.status < 400) {
-            previewImage.src = "/data/{{ object.id }}/previews/" + uuid + ".jpg";
+            previewImage.src = "/data/{{ calibration.id }}/previews/" + uuid + ".jpg";
             previewImage.style.display = "block";
             errorContainer.style.display = "none";
         } else {
@@ -74,20 +74,6 @@
         buttons.forEach(x => x.removeAttribute('disabled'));
     });
 
-    // If we already have calibration images, we show them right now
-    if ({% if calibration.state > 0 %}true{% else %}false{% endif %}) {
-        let cell, img;
-        {% for led in leds %}
-            cell = document.createElement('div');
-            cell.classList.add('cell');
-            img = document.createElement('img');
-            img.classList.add('is-loading');
-            img.src = '/data/calibration/{{ calibration.id }}/{{ led }}.jpg?v=0';
-            cell.appendChild(img);
-            grid.appendChild(cell);
-        {% endfor %}
-    }
-
     scanButton.addEventListener('click', async () => {
         scanIndex++;
         progress = 0;
@@ -126,7 +112,7 @@
     calibrateButton.addEventListener('click', async () => {
         calibrateButton.classList.add('is-loading');
 
-        await fetch('/api/calibrate/{{ object.id }}');
+        await fetch('/api/calibrate/{{ calibration.id }}');
         window.location.href = '/calibration/{{ calibration.id }}';
 
     });
diff --git a/templates/object.html b/templates/object.html
index 2ec7af2..570cad8 100644
--- a/templates/object.html
+++ b/templates/object.html
@@ -32,8 +32,42 @@
             </div>
         {% endif %}
         #}
-        <a href="/scan/{{ object.id }}">Faire un scan</a>
+        {% if calibration %}
+            <a href="/scan/{{ object.id }}" class="button is-link">Faire un scan</a>
+        {% else %}
+            <button class="button is-link" id="scan">Faire un scan</button>
+            <div id="calibration-modal" class="modal">
+                <div class="modal-background"></div>
+                    <div class="modal-content">
+                        <div class="has-text-centered mb-3">Le scanner n'est pas étalonné.</div>
+
+                        <div class="field is-grouped is-grouped-centered">
+                            <div class="control">
+                                <a href="/calibrate/" class="button is-link">Étalonner le scanner</a>
+                            </div>
+                            <div class="control">
+                                <a href="/calibrate/" class="button is-link">Réutiliser le dernier étalonnage</a>
+                            </div>
+                        </div>
+                </div>
+                <button class="modal-close is-large" aria-label="close"></button>
+            </form>
+        {% endif %}
+        </div>
     </div>
 </section>
 {% endblock content %}
 
+{% block extrajs %}{% if not calibration %}
+<script>
+    let modal = document.getElementById('calibration-modal');
+    document.getElementById('scan').addEventListener('click', () => {
+        modal.classList.add('is-active');
+    });
+    (document.querySelectorAll('.modal-background, .modal-close, .modal-card-head .delete, .modal-card-foot .button') || []).forEach((close) => {
+        close.addEventListener('click', () => {
+            modal.classList.remove('is-active');
+        });
+    });
+</script>
+{% endif %}{% endblock %}